It's probably because white's king isn't safe and can easily be attacked. White can be mated if they aren't careful.
My first brilliant move - doesn't make sense?
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White has no defenders back there, so after qe6 check, king moves, and qd2 check, white is in huge trouble whichever way the king moves. Accidental brilliancies / rook sacks are fun.
Sometimes the queen can get trapped grabbing a rook, so always look for that, but here its checkmate thats the issue.
Does this not just give up my rook?
In addition for one of my opponent's next moves the game review says he should have castled and lost his queen