The funniest part about this is that Niemann has a Chessable course that covers this very blunder. Also, interestingly enough, Hans got this exact position in March against Aram Hakobyan in the Chess.com Rapid Championship and correctly played Qe3.
Bf2 is a blunder because it allows Bxc3. White can't play bxc3 because then Qxc3+ forks the king and rook, leaving black with a better position and an extra pawn.
Niemann resigned a move later, after responding to Bxc3 with Nd2. The entire game is below:
The funniest part about this is that Niemann has a Chessable course that covers this very blunder. Also, interestingly enough, Hans got this exact position in March against Aram Hakobyan in the Chess.com Rapid Championship and correctly played Qe3.
Bf2 is a blunder because it allows Bxc3. White can't play bxc3 because then Qxc3+ forks the king and rook, leaving black with a better position and an extra pawn.
Niemann resigned a move later, after responding to Bxc3 with Nd2. The entire game is below: