I have a theory about why Vance was picked. If the Epstein files became something that actually would have resulted in Trump getting impeached, Vance is likely not in them and would be allowed to take over the presidency as puppet. As it’s become appearant that nothing is going to come of the files, or any of his actions really, Vance sorta faded away. He is also rather incompetent, a poor speaker, and doesn’t have the bombast to be Trump’s replacement so I can see why they brushed him aside.