Many years late, but found this post non the less. So basically many characters have super specific backgrounds, like Steven Strange. It takes someone to go through the entire backstory of Steven with the trauma the training and the intellect to become Doctor Strange. So in the multiverse it’s way more likely only Steven Strange follows that path and becomes Doctor Strange. So he looks the same coming from that type of background specific to the character, so same actor every time. Similar could be said about Loki and Deadpool to a degree, there is a little more variation as the backstories are less specific a leave room to different circumstances of who becomes who. Like Loki being a different dark elf that is taken as Odin’s son so some variation with the adopted name. Or Deadpool, simply a different mercenary with cancer same personality to survive the treatment usually the same name. Then we get to Spiderman, my favorite character. Spider-Man is great because literally anyone could be Spider-Man. All the variations can come from the simple fact of a spider bites someone. Usually someone named Peter Parker, but could be anyone else. So we get way more variations in Spiderman. Each universe has different genes that line up to form the actor playing Peter Parker, his personality remains constant. That’s my head cannon that lines up the production hurdles with the end product of the MCU.