Ignorantia juris non excusat or ignorantia legis neminem excusat
Mueller is a Republican.
Aside from Donald Trump, Mueller decided not to prosecute some people in the investigation for the same crimes that other people committed.
Trump Jr. knew exactly what he was doing just like Donald Trump knows exactly what he's doing. They just play stupid, just like Ivanka Trump does.
When Trump talks he speaks with very specific words that if you're not paying attention you think they make him culpable but thise specific words he used does not. He purposely repeats key words or phrases four to five times when speaking to get the message across to the base
As you see from Mueller's report Trump specifically got other people to do his dirty work, so it wouldn't come back on him. That's a strategic thinker. He didn't realize how much the people closest to him don't trust him and flipped on him very quickly because people closest to him learned very quickly that he'll turn on a dime on anyone if it fits his need in that moment that's because trumps greed and ego short circuit any long-term strategy he tries to implement in his businesses & personal relationships fail because of it.
You could be the smartest person in the world but if you're greedy and your emotional IQ level is really low like Trump, and your ego is really big like his, you'll continually sabotage everything you try to succeed, like Trump does.