My parents both have similar stories. Both had fathers that weren't around too much (my paternal grandfather was a travelling salesman, my maternal grandfather in the military) and mothers that were lonely housewives that were contacted in the run-up to 1975 and indoctrinated, and later dragged my parents into the cult in their late teens. On my mother's side it was compounded by lots of family travel due to the military father, so she was a constant fish out of water and found the instant friendship and community of the cult.
My father was raised in a small town in Texas that had (and still has) absurdly religious demographics. He claimed not to be fond of the hypocrisy and open collections taken in church and that was one of the main reasons he liked the cult. I'm sure my grandmother quitting smoking had an influence too. He's also a very emotional and humble man and I think the way the cult plays on emotion and exploits humility got him. He's a very good public speaker, but refuses to believe that this came from natural talent or decades of frequent practice but instead is explained only by holy spirit.
I've never met my maternal grandfather as he and my grandmother were separated well before my birth. I don't really know the full story, but something tells me that he didn't much enjoy being married to a cultist...at least the timing works out on that. Otherwise it's possible that the marriage was in trouble and that helped push my grandmother and mother into the cult.
My paternal grandfather seemed to regard the cult's doctrine (particularly the pandas and paradise) as ridiculous for most of his life. It wasn't until about 5 years prior to his death that he finally got sucked in - he really liked the man who married his granddaughter (my cousin) and went to his first meeting to see his first public talk. At this point he was an old man with no one in his life but his wife and my cousin and her husband, all three cultists, so all three would leave him frequently. I think he finally succumbed to his loneliness, and possibly the pseudo logic of pascall's wager (which, at his age, is almost reasonable).
So, to sum up, loneliness seems to be a particular theme here, and for my parents and grandmothers the 1975 scare definitely played a role (though they'd dispute that it ever happened if you asked them...).