The most important thing to understand about Team Mueller is that they already know beyond a reasonable doubt everything they need to know. They already have all the evidence. That’s what leads them to write things like this:
“Cohen repeatedly declined to provide full information full information about the scope of any additional criminal conduct in which he may have engaged or had knowledge.”
— Read on http://www.washingtonpost.com/amphtml/world/national-security/federal-prosecutors-recommend-substantial-prison-term-for-former-trump-lawyer-michael-cohen/2018/12/07/e144f248-f7f3-11e8-8c9a-860ce2a8148f_story.html
What they’re doing here is slowly rolling out the facts and findings via documents required by the justice system itself. It’s only possible to prove that someone has lied when you already know the truth.