Don´t think FB1 was the problem.
It was very well received (for me, it was a surprise).
FB2 opened very well overseas (yes, includind China). But legs are not good, because of the WoM.
I also think it could go much higher domestic if it had a better score on rotten tomatoes.
Maybe it could do 750M WW if it was well received.
But if they don´t change the diretor and hire another writer to help her, this series will be in big trouble.
We can´t just say "Oh, if was Rowling´s fault, not Yates".. ok, it can be true, but Yates is a medíocre director, if they want to recover the public attention, they need to do BIG changes.