I'm sure he had injuries and what not but at the end of the day, being "one of the greatest fighters of all time" doesn't lend itself to explanations like this. It wasn't like the Machida fight was his only loss. There was always talk about how Mousasi would come to the UFC and rule. He never materialized into a UFC champion, let alone defending it to justify a GOAT moniker. His resume is packed full of names and there's no denying his talent - I'm not trying to do that, but he never beat a genuinely elite fighter in their prime except for possibly Weidman and I guess WW Lima. I've read your other posts responding to this sentiment so I'm not going to try to alter your opinion, just sharing my own. There's a difference between talent and accomplishment and the 2 never seemed to align for him in the UFC. Winning belts in B Leagues is still impressive, but let's be honest, it's not quite the same.
And Machida pretty clearly won the first fight, man. I'll have to disagree there.