He didn’t pick one. The RNC always picks who they want. Endorsements mean little regarding this. That is why the head of the RNC is usually pretty rotten.
There was Reince Pribus. Remember Michael Steele? He is a darling over on MSNBC or some RAT channel now.
That’s why nothing has changed.
I remember Michael Steele all too well...he basically burned the place to the ground...Reince Priebus rebuilt it in record time...best GOTV effort and organization in 2016 the party ever had. Should have been left there vs. moving to WH Chief of Staff.
Trump installed McDaniel after Priebus left. The incumbent president generally picks the RNC chair if Republican hold the White House. They still go through the formal process but otherwise the choice is theirs.