I think his results have regressed because he is not now, nor ever been, a super technical wrestler. He won, and still wins, a lot of his matches based on his incredible athleticism. When you're young, and at a lightweight, being extremely powerful/strong/explosive/athletic is more likely to lead to wins than it is when you get older and into bigger weights. My two cents.
Not saying he's not a technical wrestler. But he's certainly not as technical as you'd expect based on his results.