Honestly, I don't think that is evidence he's guilty of election interference with the Russians, it's just that he equates special counsel investigations with dirt and bad press. And here we are, with some new dirt, and him pretending to be totally exonerated when it's clear he attempted to obstruct justice on many occasions. We know Barr's view is that a president can't obstruct justice, he was very clear about that in his unsolicited letter/job application to the white house last year. So now Barr is doing exactly what Trump lamented Sessions wasn't - protecting Trump. Obviously, that is not the function of an attorney general, despite Trump et al.'s (very poor) perception of previous relationships between the AG and presidents.
It is my opinion that enough evidence exists to impeach both Trump and Barr, but we all know the motion would only pass the house after a vote along party lines, and would die in the senate. If I had to choose between Dems winning the presidency or the Senate in 2020, I'd probably choose the presidency, but only just.