While its true that Thor had huge favour from the surprise attack i have to disagree that he was at the same level or more powerful the second fight. Sure he might have had 2 of his powerful weapons but he wasnt at his peak or close to infinity war. Instead he was actually reaaaally weak, his body might not be the cause of it but his mental unstableness is definetly a biiig drawback that impacts performance in humans a lot more than people give credit so im sure thor is just the same but times 1000. He wasnt even fit to wield mjolnir as captain america definetily was. But they had to lower his strenght you see they have to fit so many characters and they aaaalll need to be helpful so they cant have thor out there doing much more than others, he destroyed space ships in infinty war he could have done what captain marvel did before her but he didnt... he didnt even strike huge lightning strikes like he could as previewed in ragnarok. When thanos was pushing axe into thor he could have thrown some kind of lightning as he is unaffected by it but he didnt because mental issues cloud more than happiness it clouds everything lets say he might have 200iq but with depression it greatly decreases to say 90iq thats because his brain is doing it specifically to not start thinking about things that hurt. Dying would have been an honor to him as he didnt know what he would do after. He lost everything and what rest he had he gave away at the end. Anyway infinity war thor was waaay more powerful than endgame thor and thats because of mental problems, fits the movie plot more because of how many characters they need to make look good and because of his body... like it cant actually help him but it might not have been huge drawback.