Edit: I meant Republican politicans.
For the Republicans, it's pretty clear what their perspective is.
1) They have immense power right now, they are all greedily attempting to take advantage as fast and as much as they can before Trump implodes, taking them down with him.
2) A massive percentage of their base still blindingly support Trump. it'd be like a democrat criticizing Obama when he was at his peak approval. Politicians think of their own survival first and foremost, might as well hand in a letter of resignation.
3) They know that once Trump goes down, the tide will turn, giving Democrats a huge opportunity. Why would they want to take down Trump when they have so much on the line?
To them it's about winning by any means necessary: lies, corruption, the good of the american people. Nothing will stand in the way.
They all have their own very specific agendas, bought and paid for by visible and non-visible corporations and billionaires. The Repubs are all individually attempting to benefit as much as possible in this time of great power that they have before it all comes crashing down.
I truthfully do not believe that they don't know Trump is in the pocket of Russia, it's that they don't give a shit. They want to line their own pockets before they miss their chance.