Unless he gets hit by a rock in the head, gets into a car accident, something dramatic like that and he lies in a coma and wakes up a different person, then the story you're painting here (quite fast and huge change in personality after marriage) is not believable. What is much more likely and more plausible is that you saw whatever red flags he had, yet you decided for whatever reason to marry him. And then after the first child and red flags continuing to manifest themselves, you had another 2 kids. So you had the power, control and knowledge (considering your age and life experience up to that point) to stop it very early on (before marriage) or better yet, not get into it at all. That you decided to carry on for 10yrs or how long the marriage lasted, doesn't make you a hero or unicorn.
LTR, marriage those are just words describing in essence the same thing, a committed relationship. Or do you want to tell me that when you say 'I love you' during romantic moments, in an LTR you say it with half a mouth?
So if one relationship (LTR) fails, it's not surprising that another relationship (marriage) follows suit.