Mental illness. Mental illness magnified by group think. It feeds on itself and grows.
It is a classic propaganda technique: play to the fears of the unstable elements. Worked for Gobels. Worked well then, works well now.
You get a few charismatic types into power, they gain followers, their followers claim everyone else is bad/evil/sick/insert doubleplus ungood thing here. People, being sheep ny nature then follow so as to not be left out of the popular club. After a while they grow to believe whatever because they have themselves become as insane as their leaders.
End result: 150 million dead and counting.
Can’t argue with that. Watching the Left and it’s antics in the U. S. over the last 25 years, causes one to see real possibilities there.
I think you’re very close to the target there.