IANAL so really am not qualified to interpret the following well-publicized sentence from the Barr letter:

“[T]he investigation did not establish that members of the Trump Campaign conspired or coordinated with the Russian government in its election interference activities.”

We obviously do not know what preceded these words in the Mueller report but what does the term “establish” imply in legalese? Is it equivalent to “prove beyond a reasonable doubt”? Could the beginning of the sentence have read something like, “Because we were unable to conduct thorough interviews of Donald, Ivanka, and Jared”

Just idle speculation — since I am not one of the Fox anchors who have all read the original report in great detail.