In Avengers: Infinity War, when Thor is rescued by the Guardians of the Galaxy and explains his plan to get a weapon (Stormbreaker) to kill Thanos, Quill asks if they could get such a weapon too, but Thor answers that
You simply lack the strength to wield them. Your bodies would crumble as your minds collapse into madness.
In a short scene during the final battle of Avengers: Endgame, we saw Thor wielding Mjölnir and Captain America wielding Stormbreaker and then they interchange the two weapons.
According to what Thor said, how could Captain America wield Stormbreaker without being affected by it?