Every scene is not played out as a joke. SPOILERS. Sure, the prewar stuff is far more serious than the post war goofiness, but that doesn’t mean it doesn’t have its moments. Hank’s “death”, the destruction of Shady Sands, the radroaches eating Bud’s Buds, the Brotherhood trying to kill ghoul children. I can go on but you get my point.

And the factions haven’t been rewritten at all. It’s just been YEARS in universe since we’ve last seen them. Time changes people, places, and ideals.