Checked if those guys right after breaking up go pursue and date another girl?
I think what you're experiencing is common with men, specially young men: they get bored easily, and quickly go after new people.
I think "success stories" are not the most common ones, at least between young people. A couple I knew from some time (cisboy and cisgirl on their mid twenties) just broke up because she insisted so much on having a house, kids, etc. Go figure.