Why not g2 guys?

Because a knight jump takes more calories than a lady taking one step.

Because the chess engine is a snob and only wants to interact with Kings and Queens.

I've never seen a game-winning move considered a blunder.

It loses the game. White is now checkmated. The computer favours White because white has a 51% chance of winning.

Stockfish is extremely powerful, but the analysis is extremely budget cutting by using depth 10 only , which is like 1% of your smartphone power.

Imagine you choke 99% of electricity, how will an electrical applicant function?

Because the checkmate is much more brutal.

Or maybe the computer thinks that the knight moves like the "ma" in Chinese chess (in which the g3 pawn would be "blocking" the check).

https://en.wikipedia.org/wiki/Xiangqi

No, it's correct that Ng2# is a blunder.

The knight feels a little lazy to move and jump around.

Probably because if we pretend it wasn’t checkmate, Ng2 is an objectively worse move.