Do you remember when during the 2017 inauguration all those military appeared suddenly behind Trump, i believe that was a tip.
They are going to do the same thing with Biden, but they will arrest him (and several other figures) LIVE in front of the whole world. It will be the most shocking event ever transmited on live TV, so that all the world will see it.
I also believe that's the reason why the DS is pushing to do the inauguration on other places than DC.
It would also mean the MSM can't blackout the arrest. Makes sense.