I don't think the Power Armor was particularly nerfed. To put it in game terms, it was being piloted by a complete n00b while he attacked some very high-level individuals. And the Brotherhood has always been pretty ambiguous.
But yeah - it was a fantastic season and I'm glad it's been renewed.
VaultTec being the ones to stop the peace talks and drop their own nukes to ensure that the surface would be wiped clean is nuts but a neat addition to the lore.
My own entirely personal complaint:
I hate it. It's not a bad story idea, but I just would rather not know. I always thought Fallout was better because of how little we knew about what led to Armageddon. It's been one of my go-to examples of less being more.