If you ever talk to hardcore Trump supporter and ask them about many of Trump absurd ideas and comment, they will either think Trump is perfectly sane or they will say "He is just joking".
Then I ask, "How do you know when he is joking or not?"
Answer: "Its easy, he is telling the truth when I believe him, otherwise he just joking. Like when he tells people to drink bleach, he is joking, but he is telling the truth when he tells people the world is flat.."
Various political analyst have been suggesting that Trump was given several days advance warning that Mueller report was going to drop on March 22nd and he was also given a verbal, unofficial overview of the contents (no specific dertails). Enough info that he would allow him to go on the offensive to discredit the report in advance. The speculation is that the attacks on McCain are to blame the late senator and hero for some damage that is in the report. Since McCain is dead, he can't refuted any of what Trump says. The report is unlikely to reference McCain, but Trump may know enough about the report that there are several unnamed or redacted sources that provided damaging information about Trump activities. Blaming a dead man allows Trump to make up further lies that would exceed even the worst of Hollywood screenplay. In Trump's version of events McCain becomes a traitor to the US as undercover spy for foreign enemies, etc, etc, etc.