Did everyone forget that she fought against the demon king before she died and preparing the country for it (better than it was her first go around) has been one of her major objectives this whole time? Like. This isn't surprising. It's been built up since literally the first chapter. Home girl...
That wyvern leader is a good king. He knows its a powerful demon that can wipe the floor with anything he wanted- and he STILL came to talk it out. He fixxed the problem by showing a little neck and saved the lives he could. What a good dude.
Thus far I have no problem with the story. There is nothing wrong with a parent realizing they've fucked up and starting to try and do better. Shit, I'm doing that with my parent's now and I'm in my 20's. It'll be up to him, but there is a lot to be gained if he determines it's worth it for him...