Just because Leeds is the very next game, it doesn't mean the players were specifically rested for it. I wouldn't be that surprised if we rest some players against Leeds as well because following that we've got 10 games in 33 days.
Haaland, Doku, Foden have all played too much football and they have to be rested at some point.
I don't love making 10 changes and the performance of our second string is disturbingly bad, but Pep & co. clearly felt this game was one we could afford to lose, and we lost.