At least in Nebraska....
County party leaders are elected by whoever gets through the door on the day of the county convention. I was one of those (voters) in 2018. Normally, county party meetings maybe have 10-20 people for each monthly meeting. On the day of the convention, it was over well 500. Bunch of people I never saw again. It was a hotly contested election between a labor guy and a women who was more involved with campaigns. The woman won, and then the labor guy got elected to vice-chair in an inspiring moment of unity.
State party leaders are elected by the delegates selected at the county convention. (I was one of those in 2018). That was a pretty easy election for Jane. I like Jane, but she is full of shit. Our County Chair hated Jane. I feel comfortable stating that on a message board, because Jane already knows it.
National delegates are selected at the state level. (I didn't have a chance in hell of that.)
So what's my point? These are not top-down organizations. The national party does not decide who is running the state parties. Just doesn't happen. The intraparty politics are just as vicious and way more annoying than the Republican vs. Democrat politics. It turns a lot of people off, including myself. So much arguing over who gets to drive, rather than where we are going. But, if anyone wants to change who is running the state party, the first step is showing up to the meetings. Tahoe will bring donuts.