They were convinced to be cult members, as consenting adults, rather than having it imposed on them as minors by a parent, is my reading.

Later, they gained some perspective and realized it was not in their interest to stay.

I should be clear, we were both raised in it as children. That made leaving much harder. Our families are still in.

Not OP but one common example of this is staying where you live. Sure you /technically/ could move to a different country but there are a truckload of social and economic factors that keep you "stuck" in your current country. So you're stuck by choice.

There is no contradiction between "choice" and "not rational". Choices are often emotional, irrational, fear based, inertia based or result of perceived lack of choices.

people are only rational if they stop and think real hard and also are able to invalidate their assumptions. this is difficult if your assumptions are your identity, see flat earthers.