Well, Lebron won in his 2nd year with Miami and Lakers. Mahomes won it in his 2nd year as starter with not many free agents added but the defense started playing better under Spags.
Lot of things need to come together. With Brees, White, Peyton, Brady, the bigger commonality was the play of the O-line being able to run the ball to maintain balance and the defense playing at a high level resulting in key turnovers in the playoffs. That was also a factor for Mahomes and the year his OL did not show up, we saw what happened in the last SB, like with Peyton in his first SB vs Seahawks as a Bronco with not much defensive support and OL play.
Thus, the ultimate factor in all of the above instances - get good scoring defense / turnovers from your defense and have an OL that can protect the QB and help you stay balanced on offense come playoff time. Then your marquee QB can make the plays necessary when needed instead of being solely relied on to win you games.