have you tried removing elections?
Only appoint lords who are going to contribute as lords. If there are none that fit that bill, then don't make the appointment. Leave the region lordless.
Right, because no lord is so much better than a lazy lord...
I find this to be a near universal truth. Few lordship elections ever attract more than one or two candidates, and there is rarely ever any controversy or discussion about it. If there are a few candidates then you may get an endorsement letter or two from some interested parties.
I do agree that this could be due to the wide availability of titles. Getting a lordship really isn't all that big of a deal, unless it's for an important (i.e. rich) region. If it were difficult to get lordships, then perhaps it would lead to more involvement in elections. But this ties back to the whole player density thing. Increasing character count won't do anything about it, unless it is a result of increasing player count.
Indeed, character count won't change anything, because a ton of people are content with having 1 lord and 1 knight, so all of their extra knights wouldn't actually campaign for lordships and as such the demand for lordships will remain essentially the same. Likewise, those who already don't really care for a lordship won't really mind to have 2 knights. It could perhaps allow a few of the more ambitious to have both characters lords, but I doubt the impact would be worth the costs of such a measure.
Back in the days, getting a lordship used to be hard, used to be long. Nowadays, nearly all realms can advertize "Hey, join us, we have like 5 empty lordships and newbies can usually become lords within a week!", or just about.
Well, in Barca we're having some interesting elections right now. Every region is getting several candidates and everyone is writing for their candidacies, but I understand this is a rather unique situation right now. I'm sure things will quieten down once we have conquered most of the provinces, and that the noble density lowers.
There's probably special interest for some of the regions you took back, but indeed, if you keep on expanding to the rest of the peninsula... you'll be spreading yourselves thin and seeing the same.