Well, Obama followed the concept of authoritarianism much more closely than Trump, so I fail to see your point. Not to mention that less government interference in the citizen life is something that an actual authoritarian cannot stand. Authoritarianism is about control.
As for the Comey firing, the actual reason has nothing to do with authoritarianism and more to do with Trump’s cult of personality and him being annoyed at Comey. An individual who couldn’t keep his mouth shut about on-going FBI investigation.
The investigation itself was a useless waste of resources. It found nothing. Not even a shred of information that can lead to evidence, something the Comey himself noted.
I don’t know how they handle investigation at the FBI, but if they are so disorganized and lack any documentation that a man being fired could jeopardize the investigation, then the more important investigation should be of the FBI, not Trump.