I don't get why this is the "solution". To me it seems there are multiple places you could put the knight and achieve the same goal since the checkmate comes from unblocking the bishop and moving the queen in. However, the puzzle only accepted Ne7
There are only two places the knight can go that are check. If you don’t give a check with your knight, the opponent has time to block your checkmating threat. The only other check for your knight is Nh6+. When the opponent takes your knight with the pawn on g7, it blocks your queen from checkmating on h7. I hope that helped.
I don't get why this is the "solution". To me it seems there are multiple places you could put the knight and achieve the same goal since the checkmate comes from unblocking the bishop and moving the queen in. However, the puzzle only accepted Ne7