Mueller gave the excuse that the DOJ by policy can't indict a President but HE COULD HAVE RECOMMENDED INDICTMENT. So, it's a bunch of bullshit.
Mueller is a long term, bureaucrat. These people are professional slimeballs, experts at covering their asses in the corporate environment which means appearing to be responsible, without actually doing anything and then always having a way to blame someone else when things fuck up.
So his team of 100% Trump haters spent two years jerking off and did their homework the night before, when Barr told them, "hey guys, it's time to wrap this up, what have you got?"
Mueller FAILED. He did not perform. His bosses gave him ONE JOB, CRUCIFY TRUMP. But it's not like the old days when failure wasn't tolerated. These days the people really in charge are soft and don't punish failure. Which is why they will continue to get beat until they themselves are flushed out of the underbrush into the light.
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Mueller's trying to weasel out of his failure by punting to Barr. Now Barr has a choice to piss off the Deep State and be in danger of assassination, or not do anything and piss off Trump and the American people.
What's going on with Mueller is this: he doesn't know who's going to win so he's playing both sides, trying to avoid pissing anyone off too badly. He's trying to have his cake and eat it too.
But in a way, they are ALL doing the same thing, avoid doing anything that might make too many enemies.