Of course, the exchange sac activates white's queen nicely.
Can anyone explain this move to me?
If you think that's bad, that computer just called me stupid for not taking a pawn. A missed win?!?!

b3 is a great initiative for the pawn storm you're about to launch.
Also, in a fianchettoed king position, the sniper bishop is almost worth as much as a rook. Exchanging it without any knights left to defend the king leaves him very weak.
That's why often in these cases engines advise not to take the rook.
Here's another example of this:

This is from my own game against Alun Williams.
We can safely play Nxe5 because Bxa1 is losing after Ng3-Nxf5.
So black's best reply is Bxe4.
Thank you for the explanation. However, I tried to analyze your puzzle and it said it was only the best move... It's strange how computer evaluates moves
What language do you have chess.com in? ![]()
I probably would've done the good sportsmanship like thing and resigned understanding that black cannot save himself in that position
Blame it to your poor understanding then. Resinging a position where you are not worse isn't such a bright idea, is it?