
Joseph's importing of Freemasonry's death threats gave the social control a healthy start. IMO, other things that strengthened it were the introduction of worthiness interviews during the Mormon reformation, geographical isolation in Utah, ideological isolation because of polygamy, President Grant's OCD, and creative and altogether un-Christian use of doctrines about purity and authority.
Members who easily conform and have families in the church rarely notice the control, so they usually don't know it's there. In fact, much of it feels affirming to them. This includes leaders, who also have incentive to maintain the power structure. Nobody seems to know how strong the control is until they try to resist it. Members who resist tend to have no influence in the church, or tend to lose their influence. And of course, it's all God's will, so nobody questions it.
Thus, it grows and grows, and nobody in power thinks to ask whether what they think of as normal influence is actually manipulation.
Let's do this.
*****
You're never told the wording of the temple covenants until you make them because they're "sacred." Thus, control by deceptive reframing and withholding critical information begins sometime before baptism, and continues as you learn only devotional history.
At your baptismal interview, you're conditioned to let a man judge whether God thinks you're good enough. The interview questions are invasive (asking about abortion, serious crime, and chastity - they used to ask about bestiality!) and therefore punch holes in sensible personal boundaries. This begins the fusion of your identity with Mormonism. Fusion has many effects, but one of the most extensive is that it internalizes Mormonism's attitudes, good and bad. This makes the controlling attitudes hard or impossible to notice.
Authority figures, beginning with interviewers, always wear suits and often sit behind desks in nice offices. Their greater formality emphasizes their higher status, which makes you more compliant.
Mormonism defines your life. If there's a conflict between what you want and what Mormonism wants, Mormonism must win. This continues the fusion of your identity with Mormonism.
You are taught that Mormonism is the most important thing in the universe and is superior to everything. If you buy into this, the self-esteem you get from being a member can be incredible. It increases with your certainty in the church's claims and with the extent your identity is fused with Mormonism. You therefore can become highly invested in aggrandizing the church.
You are taught that nothing really matters except as it furthers Mormonism, individually and collectively. If you buy into this, you become certain that the church is your only reason for living and only source of happiness, giving church leaders tremendous leverage over you.
Many active Mormons are so dependent on the church being superior that they reactively protect their investment in their aggrandized regard for it with aggression. Further, they proactively protect their investment using persecution narratives and dire warnings about faith-destroying "lies." Thus, criticism is taboo at best, and is at worst a sign of deception by Satan. Church leaders feed this attitude by demonizing healthy doubt. If you internalize this attitude, you live in an echo chamber, further cementing every pro-Mormon attitude, including this one. If you don't internalize it, you still help other people live in an echo chamber.
Every endowed member says how awesome the temple is. Some might admit that it's a little weird, but all are constrained by social norms (internalized or not) against not speaking glowingly of Mormonism's highest achievements. Also, cognitive dissonance comes into play: it cost a lot to do it - not just in money - so it must have been worth it, right? At any rate, that's all you hear, so you expect it to be amazing. You want to go.
You are taught that every good feeling experienced by almost every human on the planet - especially peace, safety, happiness, love, connection, belonging, awe, wonder, joy, flow, and others characterized by positive self-transcendence or the absence of fear - are signs from God. If you buy into this, you suppress and avoid negative feelings that could help you determine that something isn't right in Mormonism. (And you might make public claims that become the butt of jokes among the disaffected about threesomes with the Holy Ghost.) You also interpret every good experience using a Mormon worldview, further fusing your identity with it. If you don't have those good feelings often enough, you desperately try to be more Mormon - i.e. be more obedient - in order to reclaim them.
You are taught to follow the prophet because he can't lead you astray. You're taught that the right way to deal with doubt that a commandment or suggestion is from God is to study and pray until you know that it is. Nobody admits that the prophet could be or has ever been substantively wrong about anything in particular. If you're heavily invested in the church being superior to everything, you wouldn't believe it, anyway. Some members admit that prophets sometimes speak "as men," which assuages individual and collective guilt over dishonesty.
In general, the burden to trust church leaders is placed entirely on you. They speak for God, after all, who is the source of all goodness and truth. Thus, they can get you to do anything simply by demanding more of your trust. Fortunately, their self-image as representatives of a loving God keeps them from getting you to do anything most people would regard as evil.
The church arbitrarily defines a boundary between "worthy" and "unworthy" members, and grants worthy members special privileges, status and respect - presumably on behalf of God himself. You really want to be worthy, especially if the church is everything to you. Everyone else seems to want you to be worthy, too. You pay a lot of money for it. You submit to invasive judgment for it. You would do almost anything you could be convinced is good for it.
On the day you're endowed, you have an escort or two who have already been through, and possibly many family members with you, who expect you to conform like they did. The day you're endowed is probably the day you're married or the day before you're set apart as a missionary, so you can't back out without disappointing everyone important to you. The endowment is much weirder than the rest of Mormonism, which throws you off balance, making you more compliant. You have no opportunity to back out of the covenants. You're simply told to repeat the words and bow your head and say "yes," and you're given three seconds to do it. This is all textbook psychological manipulation, whether you notice it or not.
You're given secrets to keep, which makes you feel extra special within the most important organization in the universe, but Mormon doublethink allows you to feel "humbled." You're also afforded the special privileges, status and respect that come from being endowed - and you humble-brag to yourself and others about this, too. You're thus recruited by undetected flattery into the Society of Mormons Who Manipulate Other Mormons. You start by reframing your new shared secret as sacred and withholding critical information. The more you act on the church's behalf to control others, the more invested you become in the rightness of what you're doing, and the less you classify what you're doing as control - if by the end of your endowment you could have done so, anyway.
Don't even get me started on proselyting missions.
Fin.
*****
Here's the weirdest thing to me: I really don't think all that control is intentional, just pathological.
We all choose what information to share based on what we think is representative and convincing. We even have a hard time remembering information that doesn't support our attitudes. The problem with the church in this regard is one of degree: Mormons' extreme regard for it and the pathological needs that regard engenders.
Identity fusion is the natural result of very high group cohesion. Most of us have personal identities that are fused with our family identities, for example. It's this that allows us to sacrifice so much for our children, even our own lives if necessary, even if we're typically selfish turds. The problem with the church in this regard is misapplication. Identity fusion is rarely healthy outside of family relationships. Sometimes it's unhealthy within them.
Everyone wants to feel good about belonging to a group. People tend to adopt the attitudes of the groups they belong to. Effective groups function hierarchically. Status and respect give leaders authority. Leaders usually have a more abstract but more complete view of things. Sometimes followers have to set themselves aside and just go along because it's more important that they're in harmony than that they're right. Dial all that stuff up to 11, and you've got the church.
For perspective, if you dial it up to 13, you've got the Jehovah's Witnesses.
All the manipulation surrounding the endowment, though? That's just cultish. You have to be indoctrinated and sworn to secrecy to let that slide. But because of that, it's still not intentional, at least after Joseph Smith or Brigham Young.