this may be an unpopular opinion, but this is the one bit in that whole saga where I dont want to judge him. There are many good reasons to leave a marriage even during pregnancy or if a child is just born. Marriages aren't necessarly happy just because you recently decided to get children, in many cases pregnancy actually only happen to reignite relationships even.
Of course you could argue that he should have stayed a couple of months/years to get through the initial phase with the newborn, but what then? The boys are 7 and 5. I believe there are studies that show that kids are the most impacted by a divorce when they are in elementary/early middle school age as they are old enough to understand and young enough to be scared, so I think it's good to not delay this. Plus parents that stay together but actually dont want each other (or one of them) cause usually a bigger damage than them being seperated.
Of course the big question is now how much involved he is as a seperated father, it doesnt seem much (and he behaves in public definitely disrespectful), but we dont really know in the end.