“I was wondering why the President endorsed establishment candidate Luther Strange over Roy Moore.”
Look at how many GOPe regulars Trump appointed to vital cabinet posts.
My take is that if he didn't appoint GOP establishmentarians to his cabinet, the GOP establishment in Congress would side with Democrats in making sure that no legislation on Trump's agenda would ever make it to the President's desk. I don't like that either, but those seem to be the facts on the ground. That may be why he played ball with them again and endorsed Strange over Moore - the alternative is that the charges against Moore were already an open secret in some circles and he was too much of a risk.