Without knowing the intricacies of the contractual arrangement between Sony and Marvel that has "loaned" Spider-Man to the MCU, it's hard for me to see a clear picture of what Sony's strategy with these movies has been. Because, in a vacuum, deciding to make a bunch of Spider-Man villain movies without Spider-Man (and where the villains aren't really villains) was an absolutely ridiculous direction in which to go.
But perhaps Sony is not allowed to make other live action films featuring Spider-Man while they're sharing another version with the MCU. That's the only explanation that would make any sense to me.