Doug is an excellent football coach, it shouldn’t be questioned. What he accomplished here was quite impressive, given the talent level of the program.
I think he would have done great things here had he stayed. He could outscheme most coaches, and also gets the most out of his talent (look at Nassib, Lemon, Sales, etc).
That being said, he is also extremely quirky and can be difficult to work with. His personality isn’t going to light up a room, and some people just do not like it. The two aspects of Doug aren’t mutually exclusive.
I have found that most people who excel in their professional careers are in fact demanding of others. Ask folks what Nick Saban or Urban Myer are like to work for.