Specifically, I'm confused why the game review on chess.com says this move was a blunder:
I did end up losing the knight, but that's what I expected to happen. I did it on purpose to force the king down a rank so it would be easier to attack and couldn't defend itself by castling.
I had just read Attacking f7: The Good, the Bad, and the Ugly -- Chess.com. Most of the "good" examples involved either checking the king with a bishop or forking the queen and rook with a knight, with the king as the only defender, hence sacrificing that piece in exchange for making it much harder for the opponent to defend their king. That's what I was trying to do here and it seemed like it worked out for me, as I ended up winning.
Of course, just because I won in the end doesn't mean that particular move wasn't a mistake. But I don't understand what makes my move so significantly different from all the various "good" examples in the linked article, that it's a blunder instead of a strategic sacrifice.