Why would he do this?

Been with him for 3 years on and off but had a solid 1 year together without breaking up. Anyways.. He usually isn't very affectionate, never really wanted my attention, always wanted to play his video games and whatnot, flirted with other women, didn't really care about who I was with, ignored messages, pretty much everything a good boyfriend wouldn't do aside from cheating. Bash me if you want but I stuck with him for financial stability. Within the last few months, he's been waaaaaayyyy more affectionate, higher sex drive, seems genuinely interested about what I have to say, worrying about who I'm with, where I'm going, why I haven't answered his messages when I'm out. The only thing I've really done differently within these few months is reciprocate what he did before he changed. I now genuinely don't give a shit anymore because of his lack of effort. Why would he have this sudden change? I don't think he actually noticed he's "getting a dose of his own medicine", he's too stupid to notice honestly.