The two main grievances Trump seems to have against McCain are not well-founded. If he were alive now, he would probably not answer the president. But I feel a responsibility as his friend to do so.
First, when McCain turned a controversial dossier involving Trump over to the FBI in 2016, it was exactly what he should have done, what I would have done and what every senator I served with did in similar circumstances. Serious allegations were made in that file, so McCain turned it over to the FBI to investigate. Giving the file to anyone else or throwing it away would have been a dereliction of duty and improper in our rule-of-law country.
Second, I know the president and many other Republicans were angry that McCain came back to Washington in July 2017 after his first operation to remove cancer from his brain and surprised everyone by voting against the repeal of Obamacare. But I can tell you, because I talked to him about it, that he didn’t vote that way to spite Trump, Senate Majority Leader Mitch McConnell (R-Ky.) or anyone else. People who heard his speech on the Senate floor that day or have read it since know that McCain cast that vote not against repeal of Obamacare but against the partisanship that had taken over the Senate and made it into a feckless, gridlocked, divided place.