I'm not gonna say it didn't go down like that, but it's too much of a coincidence with Spider-man involved. He'll the iron spider costume in Marvel vs Capcom can only be gotten from digitally buying Spider-man homecoming. I'm not even sure if thr costume is available in the Xbox either. I think Sony did make a deal for game rights. Can also be a coincident.Well I wouldn't be surprised if Sony urged them to do Spiderman. Also between Marvel's superheros the two most popular are Spiderman and Iron Man (at the time being). And with the success of the spiderman PS2 games, the popularity of the hero, and Sony's involvement in the character, I wouldn't be surprised if insomniac decided to go with him for those reasons. When the publisher of your game is also making a movie about the character, it makes sense to want to work and pick that hero and make a game about.
This is Marvel's push into the video game industry in a new and big way, and their first project is this game, so they might have actually gave them their pick so they can get out the biggest and best game possible