I’m curious about the same thing myself. This move seemed rather obvious (perhaps it’s looking at the leave and forward career of the piece used (sorry, don’t have the vernacular down)?
https://www.chess.com/analysis/game/live/3534963234
You may not check a game that was played a year ago, but interestingly the move that was shown as brilliant was actually the best move when I checked in analysis. Maybe chess.com saves every brilliant move made in games and add them to the engine log as "best move" or something?
Jesus we got a full on debate going on here