ahh the ole population shift myth. While it is true that the south is growing mainly to retirees, of the top 20 states by population, 12 are northern.
I have another theory. More educated people won't allow their kids to play football.
I played and would not ever allow my son to play.
While the population shift has helped somewhat, I think it’s partially that southern schools going down to the middleschool and high school have more money to hire better coaches and equip a team, but I don’t think IT guy relocating from Boston to Atlanta, or Accountant from Minneapolis moving to Charleston has enhanced the athletic genetic pool. The biggest reason for the Southern dominance is desegregation throughout colleges, high schools, middle schools, and elementary school. Going back to the 70s, 80’s, and even early 90’s, Grambling State- a Black college, had the most former players in the NFL. Today, instead of Jackson State, the Walter Payton might go to Ole Miss. Jerry Rice maybe goes to Mississsippi State, Doug Williams goes to LSU, Deacon Jones goes to Clemson, and so on...