I had a similar experience. I have a very demanding pushy cat who doesn’t like other cats because he sees them as attention competition. We got another cat 2 months younger kept him separated for two weeks and then slowly started having supervised visitation. He hissed and growled outside the door at first and then later a bit to his face. But by the end of the month they could be left alone together. This is them, about a month and a half after Ozzie came home with us.

It’s probably reduced brain function from COVID. I think that is affecting things more than people realize. Or everyone just got more greedy during that time.