I feel the same as Geoff. Mercedes and Hamilton have been winning for far too long. It was great seeing the top dogs knocked down a few pegs.
My belief is that with Hamilton, they're operating on cruise control. They know everything he likes and everything that is his equipment/ tires/ etc. A new driver throws a huge wrench in the mix and that's what happened here...sometimes the loss of one player/ personality has a marked effect on the team as a whole. Hamilton is a large persona.
Big teams make mistakes. NASCAR's "the chase" shows this all the time.