Did you read. Trump didn't hire these folks, they are holdovers. It takes a long time to weed these career folks out, it would be impossible to do so in the short time President Trump has been in office. That said, this process clearly needs to accelerate.
Oh, I am quite sure that to some here, that's just no excuse. Trump should be able to put on his psychic turban and determine immediately which ones are loyal Obamaites and which are not. Should be easy peasy to do, right? And of course, if Trump just outright fired them all, he'd be in deep doo-doo for that too.