Republicans of Knox County Tennessee Commission Hires Democrat to Lead Them

With a 7 to 4 vote, 5 Republican members of the Knox County Commission elected a Democrat member, Courtney Durrett, to lead them as chairwomen as one of their first acts. There are 9 Republicans on the Knox County Commission and 2 Democrats. Why elect or re-elect Republicans when they do not want to lead or even be in charge in the first place?
Original Video Here: https://archive.org/details/co-com-r-267-220901-reorganization