Puzzle

I don't understand. Why can't you just play 1.Qg8+ Kxg8 2.f7#?
You can't have Kxg8 when it's guarded by B at b2. So instead, you have:
I don't understand. Why can't you just play 1.Qg8+ Kxg8 2.f7#?
You can't have Kxg8 when it's guarded by B at b2. So instead, you have: