I've seen the don't want to be alone. Also alcoholics and addicts being good at manipulation and wind up being good grifters might want to marry this person for a specific reason wether it's money, shelter, favors, connections etc.
The alcoholic always winds up back with the ex he's broken up with several times probably because he knows she will cater to him/wait on him hand and foot. She knows he has 'connections' and spend lots of money on recreational activity regardless of finances. Ironically in between one of the those break ups he went with a rich girl. Part of the reason is the family had a successful business. The girl saw right through him and he was so blatant he was told do not talk business with her parents. Long story short- it's not you and there's a very good chance he'll wind up playing or using her for his own gain.
And even though you were legally divorced less than a year he had probably moved on months if not a year or two before that.