Again, he's inspired by USAgent from late 1980s comics. Cap got fed up with The Government and left so they brought in Walker. But Cap had problems with Walker so he came back as The Captain. Eventually he decides to be Cap again, fights Walker and wins and Walker takes the The Captain uniform and becomes USAgent. I'd explain it better but I wasn't a big Marvel (or Cap) fan in those days and even if I were 1980s Marvel storylines are hella convoluted, clunky, and awkward. That's one of the things I like about MCU: OK, I'm getting ahead of myself. Before MCU, when Marvel licensed characters like "The Punisher" the developers would often say "that's convoluted, clunky, and awkward." But they'd instead make some shitty compromise--making The Punisher an ex-cop who doesn't wear a skull emblem on his chest. But when MCU came along, they actually fixed things in a *good* way. Heck, even the later licensed movies. X-Men wasn't bad in the beginning; the Raimi Spidermans. If they made a 1989 Spiderman they'd be like "we have to get rid of the mask. No lead actor can be convincing in a full facemask." Tell that to Tobey MacGuire. Or The Mandalorian.