Why is it so hard for him to just co parent?

After leaving my abusive ex (father of my child) when I was five months pregnant due to his abuse, I decided to give him a chance to still be in his sons life. I did stay away my entire pregnancy and ignored his texts and calls so I figured the least I could do was give him a chance to show me he can be a decent father even though he wasn’t the best boyfriend. Our son is now almost a month old and I have agreed to allow him to see him and be around him as long as I’m there. I took him over to his place the other day, to see him for the first time. He responded well to him. He changed diapers, fed him, held him, put him to sleep etc but the only issue is he keeps making comments about us being a family. Saying how me and our son makes him want to be better, planning out our future as a family, talking about taking family pictures etc when I made it clear that all I want to do is co parent even before allowing him to see him but it’s like he refuses to accept that. And another thing is this isn’t is first child. He has two other kids with another woman but he isn’t down her neck trying to be a family. He co parents just fine with her.

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Then instead of giving all of his attention to our son fully, whenever our son would be sleep and we’ll put on a movie in the mean time, he only sleeps like three hours, he would attempt to get intimate. At one point he attempted to kiss me and then says “I wish I could touch you but I know your six weeks isn’t up.” And I again had to remind him that even if it was it wasn’t gonna happen. That wasn’t what I came over to his place for. I would I have came without my son if that were the case.
Why is it so hard for him to just co parent?
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