For all his troubles that Foreman was going through at that time, if he'd faced Spinks he'd have regained the belt ..and it would have been faster and more devastating than his first title win over Smokin !
Muhammad Ali had looked similarly crap in several previous fights in that era. He was shot, and he didn't train. I don't think he threw the fight. He probably thought the judges would come through for him again. Actually, one of the judges scored it for Ali. Ali: "I gave the best I could. I knew he was a good fighter. It was a close fight. He was the aggressor. It could have gone either way."
Ali was trying like hell to knock Spinks out in the fifteenth. He was simply too old and he'd left it too late in that bout.
Not a fix. Ali was badly hurt by the loss. It hurt him more than other losses because he thought Spinks was such an unskilled opponent. Something to that effect.
Agreed, he landed many more clean combos in the rematch and...laid on the ropes getting pounded in the first fight. If Ali had anything left (from his ATG legacy), Leon didn't belong in the ring with him at that point. I still think Ali 'tanked' the first fight.
It looks to me that Ali was trying to throw the Jimmy Young fight for at least the first 7 rounds or so, content with walking down/stalking Young without any intention of landing any meaningful punches. Sometimes we see what we want to see rather than what was actually happening at the time.