For example: Biden gets sworn in. Then, prior to Biden dismissing the the Trump cabinet, the Trump cabinet uses the 25th amendment to relieve Biden, Harris, and other members of Congress of their duties for high crimes and misdemeanors (treason, election fraud, crimes against humanity, etc.).
For Trump's statement, see 1:56 of https://rumble.com/vcpol3-president-trump-full-speech-delivers-remarks-in-alamo-tx-jan-12-2020.html
I'm not sure about Biden's cabinet picks, but I can see Kamala stabbing him in the back on day one.