Might be a small part of it, but the Flynn thing is not the kind of thing that makes people willing to take a high profile high stress position. Just the mere perception (true or not) that Trump didn’t steadfastly back Flynn is going to potentially be a problem.
Trump can’t do that one again, you’d better make damn sure that you got the right people NOW.
The MSM and the ‘rats have worked to maximize the personal “cost” to Trump nominees even if they might be confirmed. I read the other day that a top candidate who was being vetted for Solicitor General, a close friend of Sessions, withdrew his name because he does not want to put himself, family, and friends through the fires of the confirmation process. There is a real cost to what the MSM and ‘rat scumbags are doing to the nomination process.