Well, I’m here to shed some light on this (at times) mysterious issue.
Someone who is EU (emotionally unavailable) may still desire all the attractions of a casual or even committed relationship, however, they will not be willing or capable of connecting emotionally.
There can be fear at the prospect of being single again, possibly for a long time (or even forever), and with having to cope with changed financial, living and social circumstances.
There can be anger at a partner's stubborn obstinacy and pettiness, abuse, or outright betrayal.
Divorce is generally a stressful and unsettling event.
At minimum, a major relationship is ending, all sorts of routines are upset, and in the midst of the stress of transition there are legal hoops to jump through before things can be resolved.
Well at this point, the guy realizes that you really like him, he has you, and he’s no longer worried that he could lose you to another guy.