It would take 67 senators to remove him from office. There aren’t that many decent ones, and Biden has many replacements for Mayorkas if needed.
We all know that.
But evidence would be presented and could be gathered as well. More could be unearthed as to the creation and extent of this staged Invasion, and more charges lodged, specifically against his so-called boss.
And of course there is the spectacle benefit.
But the real reason is that the law demands it.