I think it has to do with this second thing mostly. Yes, they chased the record but still, this is NBA, they are prepared. Also Curry got injured, he is not the same even though Kerr says he is healthy. I think that OKC is just too athletic for them, Curry can't guard Westbrook, they don't have many easy shots vs OKC defense because they are long, both in the backcourt but also with Adams inside. So when they fall behind in a game they start playing too fast and commit a lot of turnovers which causes many easy baskets for OKC in transition, RW is unstoppable