Perhaps Rosenstein had real doubts about the Weissmann obstruction theory--any honest attorney would!--and that might explain the abusive unlimited time that was allowed to try to coerce Flynn and others into claiming something that somehow seemed like "collusion." Something, anything, to hang a hat on, even if that hat was only: We can't prove "collusion" so we're not charging it, but we still suspect it. And so we think Trump was obstructing. But as of February 14, 2019, they had still come up with nothing.
And that's the point at which Barr stepped into the picture and shut the little game down.
Will Chamberlain puts it nicely:
This shoddy legal analysis kept the investigation going for 18 months Into acts that were clearly not criminal. The damage Weissmann and Mueller have done by entertaining this garbage is incalculable.
8:45 AM - 18 Apr 2019 from Washington, DC
Of course, the real question is: Was it "shoddy legal analysis" motivated by a willingness to to act outside the law to "get Trump"?
I'd love to have been privy to the conversations Barr had with Rosenstein and Mueller.
UPDATE 1: Sean Davis sees it that way, too, re "collusion":
The breathless tone of the collusion section of the report and the blatant omission of material facts pertaining to actual Russian collusion by the Clinton campaign makes clear that Mueller and his lawyers were desperate to find collusion by Trump. And yet they still found none.
UPDATE 2: Here's my bottom line. If you read the report you'll drive yourself crazy because--if you know anything about the actual events--you're going to quickly realize that it's a tissue of misrepresentations. At best. People on Twitter are knocking themselves out even now pointing out one misrepresentation--whether by commission or omission--after another.
This is why Giuliani is coming out with his rebuttal report.
The fun will start there, and will continue when Mueller is dragged before the House by Nadler. A foolish move by Nadler, because the GOPers want nothing better than to get a chance to grill Mueller over his misrepresentations in court filings and failures to disclose exculpatory evidence. Not to mention his clear conflicts and his hiring of a radically biased staff.