The easiest answer to the question of why most star players win titles after 24 even if 24 is their peak is quite simple.
First, a players rate of improvement approaching their peak is quite rapid. Think about it: at age 16, 18 years before the peak, they were scrawny high schoolers several inches shorter, a few dozen pounds lighter, and thousands of hours of high quality practice away from a peak. The ascent to their peak is rapid not just due to the rapid physical improvement from 16-24, but because they are also developing mentally. Then, at 24, the mental development continues (slower pace; less to learn, but still positive learning). Further, the physical decline is much slower than the physical improvement preceding the peak. THis is obvious; 8 years after the peak you are 32, 8 years before you are 16! a 32 vs a 16 year old is a no brainer. The slow decline in physical continues, allowing many players to hang on until late 30s.
Furthermore, every player has 1 peak season, regardless of when it happens. It is very unlikely to win a title in your peak season, since there's only one. You just need to be really good to lead a team to a title. So when does that happen? Enter the league at 19, still with a lot to learn, still maturing physically. Maybe you hit that threshold to be a best player at 21. Rapid improvement continues until 24-25. THen slow decline begins, probably not noticeable on an individual basis and only uncovered when you look at large population stats. So a player can thus maintain MVP level play until say 32, and still be an all-star/capable of being best player on a contender until 34 or so. Now let's look: Here we have a peak at 24, say, and a window of being a leader on a title contender from 21-34. So that's 14 years of possibly winning the title as the leader. Ages 21,22,23 are pre-peak, 24 is peak, then 25-34 post peak. So that's a 3/14 chance of winning a pre-peak title, 1/14 winning a peak title, and 10/14 chance winning a post peak title. So obviously you have more of a chance to win a title post peak because you have more seasons on a slow decline post peak.
Furthermore, most NBA studs are known to be studs in the draft and are drafted by teams earning a top 5 pick. To earn a top 5 pick you have to be bad. It takes a few seasons to fill in that bad team around the edges, further making it likely a star player will win titles later than sooner. But look at the exceptions: Duncan, Rondo, Kobe placed on great teams by other circumstances, winning titles at or before their peak.
But that concept doesn't fit with our need to create story narratives. So lebron didn't win titles not because he was an amazing player on a garbage team but because he had to mature and grow and learn (and have a good team). Same for Jordan I guess (plus pippen, grant, rodman, phil jackson, etc, but shhhh...). I guess Kobe had nothing to learn? Or maybe it was cause shaq was a beast. Duncan was just super ready? Or maybe twin towers with david robinson helped. But i'm sure he would have won titles early if he'd been drafted onto boston, right!?! how about Rondo: Guess he peaked early because that's when he won his title...or he had 3 HOFers. See, team circumstances matter tremendously, but they don't fit with the fun stories.