EST-type training still exists today. You don't eat until the end of the whole weekend, or maybe you get rice and little else. Everyone is told to insult you day one until you cry. Then day two, still having not eaten, they build you up and tell you how great you are and have a group hug. Then they ask you how great you feel. Isn't this a good feeling? Don't you want your loved ones to have this feeling? Still having not eaten, you're then encouraged to pay for your family and friends to do the training, without their knowledge or consent.
A friend of mine did this training after his brother paid for his mom to do it, and she paid for him to do it. Let's just say that, though they felt it changed their lives at the time, their lives in no way shape or form changed. Two are in quite a bad place, in fact...
Anyway, point is, the people who invented everything we are using right now were also susceptible to cult-like groups with silly ideas and shady intentions.