Why aren't we impeaching Trump?
If you know the answer, why are you asking the question?
Mueller hasn't released the report detailing Trump's transgressions,... yet.
Even if Mueller released an open and shut case, the GOP House is too corrupt to begin impeachment. Only a report that is a 20 on a scale of 0 to 10 could have a shot at unseating Trump. Only if the House is flipped can impeachment have a shot. That leaves two scenarios: 1. The report released creates so much stink that Trump has to resign. 2. Mueller exposes enough Russian influence in the House that he simply issues an indictment directly, the legality of which is debatable (That would get seriously messy.) The 3rd scenario is that Trump succumbs to (take your pick) a medical emergency or assassination. Come on, CIA, do your stuff...
We're not getting out of this without a constitutional crisis and maybe worse.
It's a dopey script, but that's Hollywood (er, the Deep State) for you.
The Republican majority would never impeach their own even though if it was a Democrat having an affair then they would be doing everything they could. Its about the ability to push through the laws, policies, and regulations that they want and hes doing what they want.