To the first question, the answer is money and ego. Even middlin' men's programs pay their coaches more than Dawn makes as one of the elite women's coaches. And the title of "one of the best basketball coaches ever" vs the title of "one of the best women's basketball coaches ever" is a powerful draw. Dawn may not necessarily be motivated by either, but there will be a great woman coach, at some point, who is motivated by one or both.
As to the mootness in your 2nd point, it's not a moot point if the goal is to be better than we have been. We don't have to recruit like Kentucky and Duke, but we can't have in-state talent choosing Alabama and Tennessee over Carolina.
From an X's and O's standpoint and general _coaching_ standpoint, I think Dawn would do fine. But I think Dawn or any other woman coach would struggle on the recruiting trail for many years. I think a lot of male recruits would be reluctant to sign up to play for a woman and I'm not sure many programs would be patient enough to wait the time it takes for her to overcome that stigma.