This is some "uh, what" kind of news, but it looks like Disney wanted to have a more equitable share in the financing of future Spider-Man movies and Sony wanted to keep the contract they already had where Disney received 5% of all the money the movies were making. I kind of get where Sony's coming from, as their Spider-man movies have been massive successes in the past, but undoubtedly made a shit-ton more money with Iron Man in the mix and the ability to promote the character in the Avengers movies and etc. With Endgame having just come out, though, theoretically now is the best time to make this kind of break, even if it is kind of a bummer that we won't see Spider-man palling around with Squirrel Girl anytime soon.
I also have no idea what this means for a prospective Into the Spider-verse sequel, as that was another "in association with Marvel" things. Would be a real bummer if they don't make any more of those.