I emphasized that one phrase, because I think it’s a key reason why the MCU worked.
I’m going to make this super short, but Marvel filed for bankruptcy in 1996, and they desperately sold off the movie rights to as many characters as they could. Spider-Man, X-Men, Hulk, Daredevil, Fantastic Four…all those rights went to other studios. And when those movies because successful in the 2000s, Marvel saw almost none of the profits. (I think they made something like $20,000 off of Spider-Man.)
So when they decided to make their own studio in the mid-2000s, they could only use their less-popular characters, like Iron Man and Thor and Captain America. Since they couldn’t bank on the name recognition, that forced them to focus on quality and just making the best standalone movies that they could. And then they committed to making connected stories that led to event movies like The Avengers.
The other key element is Kevin Feige, who started producing on X-Men and Spider-Man, but also worked on bad movies like Elektra and Man-Thing. Working on every Marvel movie from 2000 to 2008 taught him a lot of lessons about what to do and what not to do when making a movie. They took a big swing on a risky movie and it paid off.
Yeah, this is a huge differentiator between Marvel and DC. Someone said that Marvel is about humans dealing with being gods, and DC is about gods dealing with being human. I think that (very generally speaking) people can relate more to Peter Parker not being able to pay his rent than to Superman being basically indestructible. Also, I’ve always like that Marvel comics are set in New York and Los Angeles and Chicago, instead of Metropolis and Gotham.