Trump has no hold on Robert Mueller so maybe for the first time in his life, Trump can't stomp on someone, can't cheat him, can't fire him, can't get rid of him. In the past, he has stomped on judges in many court cases, gone off on them in verbal abuse, etc.. Mueller is above all that, quietly doing his investigation. Because Trump doesn't know what he is looking at about him, Trump is freaking out, knowing his sordid past in business "deals" and his money/finances are being examined. If it came out Trump is financially worth less than he boasts, his ego would be shattered. If he made deals some way with Russia, that will likely come out - I would bet he had loans, has loans, from a Russian bank. A Russian rents a whole floor in Trump Tower in NYC.