I would think that that is as much a result of more international talent, the crazy contracts, and teams willing to take risks on younger players, relative to when it was typical for only upperclassmen to get drafted. The age restriction was dropped in 2007 so that surely impacts recent trends as well.
I don’t think it’s very strictly a function of age. FWIW I think very few star players under 26 or 27 have led their teams to championships.
It's a function of a few things.
One, a general rise in talent of younger players. In an age of personal trainers and AAU circuits with large bags attached, this becomes a profession very early in life, and kids take it seriously.
Two, NBA teams would rather have players train in their facilities and attend their practices instead of a college no matter what. So getting a young guy with high potential to have for 5 years and contract extend as he enters his prime is the new go to move. (The Giannis move)
Three, the G League. These teams have the $$ to spend and a place to put them. They would much rather draft high potential guys early. Getting an extra 3 years of development vs. a senior in college may turn out to be a genie in a bottle they are praying for (Anfernee Simons).
