Bad situations are made worse with changes to try and adapt to the bad situation. The original light novel is complete, but not dissimilar to what happened to Bleach near the end, the final part was extremely rushed and wrapped up everything very quickly because it's popularity had started to wane with the Japanese otaku crowd. Why, I don't know, you'd have to ask them about it. Maybe there wasn't enough gratuitous fanservice or something.
Basically, parts of this story are now accelerating, an entire volume of the novel was skipped (or possibly has been moved upwards and we'll see that story arc after this one and not before), and the plot has been changed. Because that's just what happens when you have a manga adaption of a LN that gets canned in a hurry on it's end.
That said, I think it's important to remember that Kail was 17 when all of this started and is now currently 20, because the war in his time lasted three years. His interaction with Urza wasn't good, sure. And it was changed from the LN, where he told the truth and then Urza realized that she basically tricked him into a shotgun wedding without explaining to him what that meant because she must have told him her name. But if everyone interacted with everyone else in an optimal way, drama wouldn't exist. Romeo and Juliet wouldn't have happened if literally anyone had calmed the fuck down or waited literally just five minutes before making a decision.
I doubt any of the people throwing an autistic tantrum about his bad call and throwing his entire character under the bus over it have faired any better with their own life choices. It's particularly hypocritical since, while this series of events is starting to become different, the first few manga volumes are identical the LN, which means Urza STILL tricked him into marrying her without explaining what she was doing. Funnily enough, I don't hear any of you nerds crying about that and talking about what a terrible and selfish person she was for pulling that kind of stunt.
It's enough to make somebody believe you're just looking for things to complain about.
Which you are.