Venom and Spider-verse went to their heads, now they get to turf out Holland's Spidey as is Sony tradition
I mean, you're totally right- Venom and Spiderverse definitely went to Sony's head, but can you really blame them? Venom made over $800 million worldwide (despite very poor critical reviews) and Spider-verse was universally beloved and won the Oscar for best animated feature (and don't forget that FFH recently became Sony's highest grossing movie of all time). If there was ever a time for them to play hardball with the movie rights to Spider-man, this is it!
Put all of that up against Disney's current (but also justified) hubris and greed right now, and it's a perfect storm for these mega corporations to have a pissing contest over this extremely popular superhero (and the millions of dollars both companies want to make off of him). I definitely don't like it (Spider-man is my favorite superhero of all time and I've loved all of his appearances in the MCU), but I understand it.
Also, it's not like Tom Holland is just getting started as Spider-man- he's made five appearances in the MCU already, including two solo films. No MCU character has gotten more than three solo films (until Thor: Love and Thunder comes out, at least), so it was unlikely we were going to get several more "Tom Holland as Spider-man" solo films, even if the character did stay in the MCU.
It seems like the worst case scenario is a Spider-man 3 movie from Sony that feels just like (and hopefully is just as good as) HC and FFH, but they just can't mention or show any past MCU events or characters that Spidey has been/is connected to (which is a small group consisting of just Fury, Hill, and Happy, since *spoilers* Iron Man is dead). They could pretty easily make it work that he is disconnected from the MCU world at large, based on what happens in the FFH mid-credits scene.
At least, these are all the things this mega-Spidey fan has been telling himself since this news shocked him yesterday afternoon!