Because he didn't want to go to jail, that's why? like John Dean did as White House Counsel under Nixon. Trump isn't likely to go to jail no matter what but many in the white house who have lied about Trump almost firing Mueller could still go to jail over all this eventually. So, Don McGahn doesn't want to go to jail, be disbarred just because Trump is being an idiot like what happened to John Dean under Nixon. He's not only saving Trump's ass he is saving his own.
Not only was he and is he saving Trump's rear end and his own rear end. He was and is as a by-product preserving our democracy so it doesn't become a dictatorship under Trump.
The people around Trump need to be very careful what they say to the special counsel and if they don't have a lawyer they should get one soon. Because they are all the ones who likely could go to jail. Remember, Nixon didn't go to jail he was pardoned by President Ford who was his Vice-President and became president when Nixon resigned. But, Haldeman, Erlichman and Dean did go to jail who were in the White House with the President.
So, people in the White House around Trump are likely the ones who could go to jail this time too.
So, no matter what Trump tells you you must cover your own rear end because he is not loyal to you because he is paranoid just like Nixon was. Trump isn't going to protect you at all. Look how he throws everyone under the bus so far!
Actions speak much louder than words!
He was confirmed on June 24, 2008 by the United States Senate and was sworn in shortly thereafter. He is credited as having played a crucial role in loosening regulations on campaign spending. McGahn resigned from the FEC in September 2013. After leaving the FEC, McGahn returned to the law firm Patton Boggs.
https://www.npr.org/.../the-quiet-man-the-powerful-conservative-white-house-lawyer-in-...Jun 6, 2017 - By day, Don McGahn is a straight-laced lawyer, but by night, he's a long-haired rocker. In the White House drama that occupies almost every news day — from the firing of the FBI director, to the Russia probe, to the controversial travel bans — there is one crucial name that hardly ever is mentioned publicly: ...