WASHINGTON—Robert Mueller’s long-awaited report is unambiguously clear on this point: Russia interfered in the 2016 presidential election and sought to help Donald Trump win the White House.

That has been the unanimous view of the intelligence community for nearly 2½ years. But it is laid out in unprecedented detail across nearly 200 pages of the special counsel’s report, which also describes Russian efforts to forge ties with members of Trump’s campaign to further the Kremlin’s interference goals.

The...