Hi. Well, im a pragmatic person and yes the emotional roots of an issue is problematic *when its not addressed* so to me, you already, if unintentionally, have a partner (who just told you) he has got past that first hurdle. So forgiveme for being blunt but, as to that question “why (did he do an about face)”, its more like, who cares? Let me explain:

its in the past and the fact is that his actions (being one way for 2 month then actively seeking a positive change) has got o to step two, whereas your question “why” is like a  step backwards: The fact that someone is making an effort to be a team play and fix and help your relationship grow is 1000x more important and you should get on that page too. to ask him, why, and to distrust his face-value answer of “because i care about this relationship” shows your dismissiveness and devaluation of his true feelings. i hope you get past that “why” and actually work as a team to build positivity instead of sewing doubt and negativity.

Perhaps couples counseling can be a short-term way to assist growth between you two.

Best of luck!