I get the feeling that those calls and letters had not been done because Kelly was afraid that Trump was going to fuck up, so he told him “Obama didn’t call either you don’t have to do it”.
So when Trump was confronted, he said that he always called unlike Obama. After saying that, he was forced to call, and having the delicacy of a rhinoceros in a crystal shop, he fucked up big time. And now he is mad a Kelly and ordered him to go on camera and clean up. Kelly had to burn his Gold Star Family card, which would have been handy later when the indictments for corruption in the Trump administration start flying.