Impeachment is Congress using its privilege to check the presidents actions. In reality, all it does is say "We think you did something wrong, here is the evidence". It doesn't remove the president from office. However, it does set up the process for removal; should the charge be sufficient enough for the senate to vote on removal of the president.

Why hasn't it happened? Bedsides being Trump, what has the adiministration done illegally? I mean, yeah his policies are stupid and he's a fucking loud mouth, but every charge leveled at him has proven to be false or obviously not enough for proceedings to even start, proven today by that embarrassing vote from that moron Al Green.