Really?
Here's what Mueller actually reported about Trump and his son. I'll give you the page numbers. You can follow along at nyti.ms/2JaiWuZ. /1
Don Jr. writes back: “If it’s what you say I love it ... Could we do a call first thing next week when I am back?" (Mueller report, Vol. 1, page 113) /3
1) Don Jr. colluded with Russians to seek election help.
2) Trump and Don Jr. tried to cover up that attempt.
3) Trump, knowing of the attempt, tried to abort the investigation of what the Russians had done.
Mueller didn't exonerate Trump or Don Jr. He nailed them.