Joe Biden hasn’t been thrown under the bus, he fell out the back door as a victim of circumstances on the road to MAGA. He’s a tumbleweed now, back there in the desert of the political landscape.
I think he jumped off. When his own party refused to support his run for a second term, he endorsed Kamala as revenge, knowing they wanted to primary someone, knowing she probably wouldn't win... when Trump was sworn in and welcomed back to the White House, Biden looked positively delighted. He's the Après moi, le déluge type. His family's secure. He doesn't care what happens now. He wanted to screw the DNC for not supporting him, and it worked beautifully.