My friend was married to a man who was very clear he didn't want children.
She begged and begged until he gave in, but said in no uncertain terms that she shouldn't expect him to be a hands on father.
Thing is, as soon as their DD was born he simply feel in love and turned out to about as hands on as it gets. She's absolutely the apple of his eye (and about to turn 18 now so not a flash in the pan).
He still says how grateful he is that his wife "made" him agree to have a child and how much he loves her for not giving up on him.
So, it can work the other way around, though IME this is a less common scenario.
Part of it I think is just that people think it's just what you do. Get married, buy a home, have children and just live life on autopilot without really thinking about it.
The other thing I've noticed is the issue of maturity. I've known couples where the woman is ready to have children and the husband is still acting like he's in his twenties when pushing 40. Unfortunately time is in mens side when it comes to fertility and that frankly been an issue in having children at their wife's pace and not their own. Quite a few have become good fathers to a second family, whilst being shocking to their first simply imho because they finally grew the fuck up.
All that said, unless a man is pressured into having children then I think it's really hard to guess what sort of parent he will be. Men I thought would be great fathers turn out to enjoy anything and everything above being an active parent and the same in reverse.
I know blended families have their own challenges but one thing I was 100% sure of was that DH would be a good father to our children because he was such a good father to his existing child (and an effective co-parent with his ex and didn't low ball her on maintenance because he wanted his child and her mum to have a good standard of living).