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to sookenneth : Bishop x Bishop interferes with backup that Queen recieves from Rook. Allows King some other moves.
If black goes 2 ... g6. That saves the situation for black isn't it?
It doesn't really help. If 2...g6, then 3. Bxg6 h6 4. Qxh6+ Kg8 5. Qh7#. Mate in one less move than the puzzle solution.