To answer your question, true collusion with Russia is indeed a serious matter, such as what we’ve seen with Obama/Clinton and Uranium One.
Rush is also attempting to use a reality distortion machine, to claim Swamp creatures didn’t know about the corrupt DOJ. He/They just thought the corruption was so deep, and so committed to nail Trump, that Trump was in serious jeopardy. And he still is, to some extent, but the tide is starting to turn, thanks to the Congressional committees, and conservative media exposing Uranium One, Strzok, etc.
The Democrats always accuse their opposition of what they are planning and doing.
This serves several purposes: (1) it diverts attention elsewhere, (2) it slows down recognition of what they were up to (3) it makes it more unbelievable when the truth finally comes out, because ordinary people have a hard time believing a national party would tell such stupendous lies, and (4) when the furor dies down, they can engage in the same behavior again because rank-and-file voters only remember that the Republicans did it too.
Of course, this strategy can only work if you have the MSM in your pocket, and are absolutely sure they will stay with you no matter what.
If a Republican tried this, he would get shot to pieces instantly.