ROC & Avigdore
If you read Barr's initial 19 page interview memo he lays out repeatedly that Trump has not committed obstruction even while Barr remained "in the dark about many facts". Barr's own words. Barr had previously decided that if there was no evidence of collusion there was no obstruction. That is why Trump nominated him. Barr stated in his memo, "Mueller's obstruction theory is fatally conceived". Barr should have recused himself for conflict.
Here's a pertinent nugget from Barr's memo "Mueller's overly-aggressive use of the obstruction laws should not be embraced by the Department..."
How far you must have your head Trump's ass to believe Jeff Sessions wasn't fired and Barr hired solely to thwart OoJ charges...well, it depends how narrow your hips are.
Secondly, if ever there was a case where a President's actions call into question the bounds of Presidential prosecutorial discretion, lawful exercise, or executive constitutional authority, this is that case. Fact: Witnesses in the collusion investigation destroyed evidence, used encrypted communications during the investigation to avoid oversight, and stonewalled investigators. So much for the "most transparent" BS Trump spouts.
I need to read Mueller's report again to see if there are hints of this, but use of encrypted communications while serving in the administration, according to Hilary server screechers, illegal.