Sony, on the other hand, just kind of wanted Spider-Man. And while Sony probably wouldn't have skimped out on eventually making an Iron Man or Thor movie, they'd have just been supporting players. It didn't help that Avi Arad, who was the head of Marvel's film division at the time and had a close relationship with Sony, was suuuuper into Sam Raimi's Spidey trilogy and not much else. Arad had said, "But if we want to do that, the crossovers, it has to be a story that is centered on Spider-Man. We cannot be second banana to anything out there." Legend tells that if you whisper "Tobey Maguire" into a mirror three times, Avi Arad appears to sign you up for a multi-picture deal.
The point is, if Sony had bought the rights Marvel was offering for peanuts, Marvel would have never been able to self-finance their own movies, and we would've never seen the rise of Kevin Feige, who put the MCU together in a way that seemed taken directly from our middle-school dream journals. We might have gotten The Avengers at some point, but not in anything like their current form. And we definitely wouldn't have Infinity War. Instead we might have Spider-Man 10, which would just be a two-and-a-half-hour montage of Willem Dafoe talking to himself in a mirror.
It's astounding how all that worked out. This is the kind of thing that derails other franchises all the time. The Bond series couldn't even use the villainous group SPECTRE for decades due to legal battles, and only got the chance to after Skyfall. And when it got there, they soon found out that a gritty Daniel Craig series doesn't exactly mesh with a octopus-themed cartoon terrorist group and a Christoph Waltz performance that I can only describe as "violently indifferent."