The fundamental principle in king-and-pawn endings is that you want to get your king in front of your pawn(s). If your king is behind your pawn then your opponent can block with their king much more easily. Therefore 2.Kf1 is a mistake, because it allows the white king to get in front of the pawns and also attack the black pawns. Whether it is a game losing blunder I'm not so sure, but it does make winning much more difficult. Either 2.Kd1 or 2.Ke1 would be much better with Ke1 being my favourite as it stays in line with the middle pawn.
In general, white's winning plan is to immobilize the black passed pawns and then start winning the pawns when the win becomes easy.
Here's what happens if black still tries to penetrate with 2... Kd3
[fen "7Q/8/8/8/p2pkp2/Pp2p3/1P2K3/8 b - - 0 1"]
1... f3+ 2. Ke1 Kd3 3. Qh7+ {It is vitally important to keep the white king out} Kc4 4. Qf5 {Still keeping the white king out and threatening the f pawn} f2+ {only move to hang on to the pawn for now} 5. Ke2 {Zugzwang! The black king has no moves} f1=Q 6. Qxf1 Kc5 7. Kd3 {and the two center pawns will soon drop}
So the immediate 2... Kd3 is a mistake. Can black still manage it by first driving the white king to f1? Now white can keep maximum pressure by bringing the queen to e4 forcing black to keep defending the e5 pawn, because if black allows Qxe5 with Kc2 going after the b2 pawn then the queen also defends the b2 pawn.
[fen "7Q/8/8/8/p2pkp2/Pp2p3/1P2K3/8 b - - 0 1"]
1... f3+ 2. Ke1 f2+ 3. Kf1 Kd3 4. Qe5 Kc4 5. Qe4 Kc5 6. Ke2 {forcing white to abandon the c pawn} Kb5 (6... Kc4 7. Qc6#) 7. Qxd4