When an American hero dies, even if he was your political enemy, you do the right thing and you thank and praise him for his service...unless you're President Trump. He couldn't quite bring himself to do it for John McCain.
The two men who defeated McCain's runs for the presidency, President Bush and Obama, both of whom fought with McCain often and sometimes harshly, will be delivering his eulogy.
That's how it's done.
The president is a small man.