1. Joe refused, which shows how much he is still pissed to be pushed aside
2. Joe is incapacitated, and they can’t admit that the guy they were insisting was ready for four more years was instead on death’s door
3. They don’t want Kamala in the end so they don’t want her to be in control of anything yet

I believe the extreme coordinated fanfare for Kamala is a trial balloon to see if the public rejects her so they can open the convention to others. But it does look like they will stick with her given the response from lifelong Dems who are showing they wanted anyone but Joe.