7. "Favreau had already done Elf and Zathura by that point. " In response to In response to 3
He'd already transitioned into big studio films before Iron Man.
Marvel started with established studio directors (Favreau, Branagh, Johnston), then started using folks better known for TV (Whedon, Alan Taylor, the Russos). Guys like Shane Black and James Gunn started the transition to "indie", because while they'd written screenplays for the studio system and directed minor works, they'd never done anything of that scale before.
I think Jon Watts for Spiderman: Homecoming was the first *real* indie pick from Marvel. He'd never done anything for the studio system at all, and then got handed the Spider-Man franchise. Pretty amazing.
After that's when they transitioned to Taika, Boden/Fleck, now Zhao, Shortland, etc.
There are a few examples of Marvel-to-indie directors before the MCU, but that's not much of a surprise, because it was spread around a variety of studios and no one really knew what they were doing. Sometimes it worked out (Blade II to Guillermo Del Toro), sometimes it didn't (Fantastic Four to Josh Trank).
But I think MCU's transition to indie voices is especially noteworthy because the machine is so large, and it's so easy for voices to be lost. Some of them have shone through (Taika, Black/Gunn if we want to argue for them), others have just gone along for the ride. It'll be interesting to see how this new batch does for Marvel.