Yeeaahh... you were trying to argue that since Brady fell behind 28-3 to the Falcons, that he "disappeared" in a big game, but when you actually find a way to come back and WIN that game and that game happens to be the SuperBowl, I think you get a pass.
You also get a pass when, even if Brady had lost to the Falcons, he would have still had 4 rings and 7 SB appearances and his greatness would never have been questioned. Mahomes has 0 and 0 and until he actually does something noteworthy like advancing to the SB, talking about a "great half" is about as useful as talking about how good Gordon was at certain times for us this season.
And yeah, him high-fiving fans after crapping the bed in the 1st half of the biggest game of his life, only to go on and LOSE does make me question his killer instinct. Only time will prove me wrong or right, but I'm pretty confident I'm right.