Because he was hit and it was way short. He also went down and got the low snap. There is no reason why anyone should but that of Fitz.
Don't be stupid. Bad snap and bad blocking causing him to be hit on the arm as he threw. How is that his fault?
Some posters are just blind and look for any reason to blame Fitz. Dude isn't great but no INTS in the 1st two games and a lame INT today is not bad.