The Electoral Count Act states that the presiding officer during the count of electoral votes shall be the President of the Senate. The Vice President has the official role to be President of the Senate, but it can be assumed by the President Pro Tempore of the Senate if the Vice President is absent. The President Pro Tempore is elected by the Senate. Usually the position is held by the most senior senator from the majority party. On January 6th, 2021 the post was held by Sen. Chuck Grassley.
Prior to Janiary 6th, 2021, Grassley made a statement that he would be presiding during the electoral count. There appear to have been a variety of schemes underway to cause Pence to be absent (including the attack itself), but Pence did not go along.
Celebrating the possibility of constitutional chaos didn't use to be a common thing on this website.
Pretending that the 2020 election was legitimate is foolish at best.