Young QBs are like a roller coaster ride. Nix had open field to left which would give them a first down. He elects to trust his arm and heaves it down the middle with a WR bracketed by 3 DBs. Pass was defended. Now puts his team in a tough spot.
Two things. The Bills D line to put pressure and contain Mahomes. Allen to get his head right and trust his teammates. Those two things will put the Bills in position to win.