With spiderman its just a simple fact that every movie has made less than the last and that is not the direction you want to go in with an IP that has that kind of potential.
Sony could have just got their shit together and tried to make the best Spidey movie they could but that was still no guarantee that they'd get the returns they'd want. Their best bet was to have Marvel take the wheel and give Spidey the kind of buzz he would get from joining up with the Avengers. They can get that MCU cred and also have a (hopefully) decent Spider-Man movie to build a new franchise on.
I'm just gonna hang back, and wait for you to respond... since we're on the same wavelength it seems