It's weird. Maybe AO was a goodbye slam for him. I was surprised that he won it and his foot held up.
But if you look historically, his foot/knee have NOT been holding up for hardcourts and grass for the past several years. He gets injured playing consecutive tournaments on those surfaces.
Unfortunately, now however, the same has started happening on clay. This is the first time I recall that he hasn't been able to finish even 2 consecutive clay tournaments without injury, even after coming from a long lay off.
Nadal still has the tennis, but his body seems to have given up. 21 slams is pretty darn good, and even if he retires soon, he would be in top 3/top 5 of any GOAT conversation in any era. So no use pushing it IMO.
Ultimately, it's poetic justice. Fed came first and set GOAT benchmarks. Then Nadal came and ultimately surpassed him. Next came Novak who will eventually will leave both behind, and deservedly so..