I wonder how these psychopaths can sleep at night who run these cults.

That's easy.

Sleeping at night isn't a problem for psychopaths.  They have no remorse or conscience, so nothing bothers them.  I grew up with a psychopath (my father) so take it from a lay-expert.  These types sleep well and they have no problems in life except being concerned about getting their own personal needs met.  That's usually when they cry, too -- for themselves -- when their needs aren't getting met.