It must be pretty fascinating to live in a timeline where you already know everything that’s going to happen. That’s what Steve Rogers, a.k.a. Captain America, was going through. So, when someone tells the Cap that there’s a certain hammer that nobody can lift, he already knows who’s going to pick it up.
Himself, that’s who, and he does so in the final showdown in Endgame. He already knew what was going on in Thor, and if he wanted to, he could’ve traveled to New Mexico to pick it up and show his worth. That smile. That danged smile.