Actually many of the thugs end up being killed by the people they help into power. The last thing a totalitarian government needs is trouble makers.
The brownshirts were one of the targets on the night of the long knives. Not all were targeted, just the ones who were likely to be problematic. Che Guevera fled Cuba after helping Castro to power for the same reason, he knew Castro would kill him.
You are right.Stalin killed all the “revolutionaries”.
Thugs are only useful so long and then they are no longer “useful idiots”....hmmm, sounds like the clintons took a page out of that playbook!ha.