I mean surely you just have it reversed, An alien being of dubious morality landed his museum right near Disneyland so The Avengers built a facility near by to keep a close eye on it, seems to make sense to me as much as any other theme park land does. As for the Spider-Man ride, it's nice to see Tom Holland will actually be in it, I seem to recall the big info dump for Avengers Campus happened right at the same time that the Sony deal fell apart so there was some question over how much Disney would want a Spidey they didn't control in their ride. I highly doubt the ride will be better that Islands of Adventure's but I certainly hope it is, I love super heroes and theme park rides and want more super-hero themed rides and it is kind of depressing that the one I have been riding for over twenty years is still basically the best one.
Also does anyone know what's up with the actual Avengers ride? It still seems crazy that they are opening a land with Avengers in the name years before they have an Avengers ride ready, and I thought opening Galaxy's Edge like 9 months before the main Star Wars ride was a bad look, but I am kind of hoping that Covid delaying the land's opening by a year or more will end up shrinking that gap but I'm not sure how much work has actually been done on it.