[user104658]

Actually the saviours don't seem to have much of a criteria for who they take in, other than that they won't be defiant. I'm sure they only killed the oceanside men after they tried to fight back / stay independent? And then the offer was given to the women again after all the men were killed, but instead they packed up and left.

Really he was a prime candidate for them. Someone broken and desperate with nothing left, who would happily "be Negan" after being... "saved". Most of their loyal followers seem to be people who were struggling "out there" on their own and were taken in. Easy to manipulate and gain the unquestioning loyalty of someone who has nothing else left and is desperate for somewhere to belong.