The thing is Andries, people do get sucked in because that's the nature of a cult.  Its nature is to appear harmless to all new people and yet suck them in deeper and deeper before they realise what's happening.  By the time they're inside the vacuum cleaner, they can't see the world properly any more and don't even know they're stuck inside a hoover bag.

People then come and shout at them from the outside and try to tell them they're stuck inside a hoover bag but there's so many other people stuck inside the hoover bag with them that the people outside seem irrelevant and outside of reality.