capitalist excess. the concept of a shared universe between massive Hollywood blockbusters is cool. Even better if you can spin it into different media types. A huge shared universe is cool!
Oh fucking woops you did it too much and now there's 300 hours of content to watch, and its all the same shit. mediocre movie with a post credits stinger. over and over again.
a restrained approach probably would have unironically stopped after the first avengers movie. they achieved their goal by then, everything after is just excess.