Like a poster abovre said, prison. He learned how to mind control people. The drugs made them more suseptable.
From what I’ve read from his followers, he seemed to be able to read their minds. Now this didn’t work with all, there were those few who were willing to kill for him, they did and got the attention, but theres not that many who would.
Manson was known for his slick and facile style as an adolescent when interviewed by social workers. In prison the powers of manipulation he learned to survive made him omnipotent on the outside.
It still happens with Manson and regular serial killers even to this day. It isn’t uncommon for women to befriend and even marry heinous criminals while they are in prison. Manson still has a strong amateur cult following. I watched an interview with him once and his personality certainly came across. He is still batshit insane but also fairly articulate and very aggressive. I can see how some weaker people could fall for that. If he were released today, he could probably have another full-fledged cult up and running within a month.
Ask Osama Bin Laden.
I dont think its very hard. You get unstable people angry enough and they will kill, some of them were just looking for an excuse to do so. ObL was trying to start a war with the west. People who dislike Americans are willing to kill for him. Manson was trying to start a race war (which was referenced by the name Helter Skelter). People who disliked blacks joined him. The rest were taking part of his guru status and listening to his belief that after the race war, they would emerge from a secret hidden underground world, and be worshipped by blacks (who will win the race war) for their whiteness and be allowed to run the world.
That was the theory. In the end they ended up shooting a black drugdealer than started killing celebrities. So much for Helter Skelter.