I think it's simply that streaming has devalued the theatrical experience for many. Once people suddenly got THOUSANDS of movies available "for free" with a subscription, it made both going to the theater and renting a film feel too much. The short 45 day theatrical windows helped condition audiences to "wait for streaming."
Of course, studios are FINALLY realizing that streaming isn't nearly as profitable and you can't really justify spending $200 million on a movie that's meant to go straight to streaming. Initially, it was worth streamers spending a fortune on expensive shows as they were trying to lure more people to the service. But now most streaming services have kind of maxed out on the amount of people they can get to join, so all they are trying to do now is retain subscribers.
I think audiences will suffer from the streaming pivot in the long run. They want lavish, $200+ million movies but they don't want to pay for them. Eventually the movies they claim to want to see will stop being made.