I'm not even sure is the balance reason for low population. For example, the most populated native server is neoGK*Siege_best which is a copy of original neoGK*Siege which now has third of its original population. What is the reason for that? neoGK*Siege_best is run by former member of the same clan as original server but the thing is, he's Turkish and server is located in Turkey. This game is predominantly played by Turks and eastern Europeans.
Another example is Sebastian's Battle of Europe mod. Very similar to cRPG but different and improved in many ways. Less errors and glitches than both cRPG and Native. Improved graphics. Had short surge of low population, right now effectively dead.
Point being is, when chadz announced M:BG, Turkish part of Warband/cRPG population wasn't pleased. Their clans abandoned the mod awhile ago. Followed by bigger part of large eastern EU clans (Druzhina and Greys). Only remnants of those clans still play the game.
It is all about being able to pull large amount of people to your game. Chivalry guys had (barely) successful Kickstarter during golden age of games crowdfunding. But they managed to sell million of copies because: a) they are American developer (this is very important, Witcher 3 will never sell as much CDProject wants because they aren't from USA), b) they emerged in a limbo where Warband was moderately old and weren't many similar games (WotR was huge fail).
I don't think so that things will go well for future new games in this genre, market for them isn't growing because no one who can make it grow isn't making these type of games (like Blizzard). Mount&Blade is recognized brand and Bannerlord will sell same and better, no matter what. Rest of the games are on their own. I'm afraid that not even quality of the product is enough to make a new classic. Sebastian's mod isn't perfect, but doesn't deserve such quick death (serious effort was put into it). And we all know Natural Selection 2, best game no one plays...