Why do some relationships seem to go great for a while but once a kid is involved it all seems to change and sometimes fall apart?

Having a child definitely helped me realize I wanted better for my son and I.

Because a child is alot of responsibility and dealing with one can show a persons true colors.

People also can get bogged down by the constant stress. Sometimes just wanting to escape.

Maybe they got into a relationship too early and didnt expect the child. Then they feel tied down to a life they didnt expect.

i guess they weren't ready for that aspect and change in dynamics and revolving of attention to the child