One of the perks of a theocracy is that a ruler can appoint themselves as duke. This has happened a couple times, with both Rowan and Ysgarren. I *think* Alexandria had planned to appoint herself somewhere, too.
Other than that, all of our government positions are elected. You can't blame the people in power for continuing to get elected to their offices. It's the entire nobility of the realm that elect the council. If they want to keep electing the same group of people, then they will. For example, Brance got wounded in the same battle that killed Rowan, the former ruler. Two people announced they were running before Brance recovered. As soon as Brance recovered and announced his candidacy, one of the other candidates immediately withdrew. Brance won in a landslide, with less than 24 hours for the realm to set their votes to him. Is it Brance's fault that the realm wanted him to win?
As for Gelene, that was a bit of a "Hurry up and appoint NOW!" situation. After Duke/Vasilif Rowan was killed, a rogue SA priest drove the only knight of the region out of his estate and it started to go down hill fast. I needed a duke NOW to get the region back under control. It just so happened that Melania and I were the only ones around. Poof, instant duchess. Not that I think Melania is a bad choice. She's actually a good choice. I just didn't have time to do a realm-wide search, then wait for the candidate to travel to Gelene, while trying to fight a war. So I had a noble whop was suitable, close, and willing.
And, really, this kind of thing is not all that unusual. The people that tend to stick around and make themselves noticed are those that tend to get elected and appointed. And as I have mentioned before, those that are willing to step forward and take up the positions are those that will get them. Melania volunteered herself, so I accepted. I did have one other volunteer, but it wasn't until after I had already accepted Melania's offer.
IMO, I think this is really one of the keys to getting duchies, and positions in general: Knowing when to put your name forward. You have to actually put yourself in the spotlight and make your name known. It's all about name recognition. It is very rare for a quiet, unknown noble to get a lordship, let along a duchy or council position. If it comes open, volunteer. If an election comes up, run for office and make your speech. Take part in realm-wide debates. Become a marshal. Try to get on realm councils.