I would guess that this was one of the things that could be done quickly to show that Trump is 'doing something'.  

Considering the attention span of those who aren't political junkies, being able to show those who voted for change that something was done will help satisfy them.    

Obama did similar instant things when he came in.  

"Within hours of taking the Oath of Office, President Barack Obama ordered all federal agencies to suspend all of Bush’s eleventh-hour rules changes, pending a full review."