If you maxxed out your potential at a young age, you are more likely to have broken some things, which initiates the decline through nerve damage and so on. Also, the nearer you are to your full potential being maxed out, the sooner the decline will become noticeable. If you are just coasting at 60-70% of your potential in your 20's and 30's, you may not be aware of the decline happening until 40's-50's. Your ceiling is coming down, but you are still able to shift into higher gear, thereby keeping a similar or higher cruise speed. Then at the convergence point of that rising rpm meter and the lowering ceiling, that's when you will become aware of the decline that has been building for years, and it will hit like a ton of bricks all at once.
alpha chad vs beta latebloomer chart attached