Control Calradia in about 10 years, the snowball problem, game difficulty and presenting my playstyle

[Apocal]

Because it's supposed to be a semi-historical game? What's the point of the game if there is no challenge.

Because there are better ways to provide challenge than a giant campaign-level rubber band snap.

 

[Kentucky 『 ＨＥＩＧＵＩ 』 James]

Because it's supposed to be a semi-historical game? What's the point of the game if there is no challenge.

Rebellions and civil wars are not caused by rapid expansion, or different culture rulers. The Mongols conquered almost all of Asia with no civil wars and no major rebellions. The crusaders were held up by muslims as a model for tolerant rulership, and they also had no rebellions or civil wars despite ruling over a mostly non catholic population. If you look at major rebellions in history, even in the modern age, they're caused by governments not following the rules they've set out for themselves, like introducing new taxes or making grain to expensive. Almost nobody prior to the 1800s cared that they were being ruled by foreigners, or that the empire they were in was too large.
You can say "big empires are unweildy", but the Roman empire was bigger than the USA for some 500 odd years, far longer than any country today, big or small, and for most of that period, open rebellions were very rare.

The sheer volume of rebellions and civil wars in video games is something that appeared in some strategy titles from the 90s as an attempt to lengthen the campaign. Many of them had small maps or passive AI, so they wanted a way to slow player expansion in a way that felt more natural. But this is no longer necessary, and most of those old games are annoying to play nowadays. There are a million other ways to make a campaign challenging without making it drag out like that.
For instance, the original Shogun Total War had a brutal AI that didn't cheat at all, and would give you a real asskicking in battles. Therefore once you were the strongest faction, you would automatically win the campaign.
Similarly, in the original Rome Total War you could rapidly expand across the map if you knew how settlements worked and could manipulate population and public order. You never had to slow down at all if you knew what you were doing.

Forcing the player to sit around with huge garrisons while public order goes up is not only laughably ahistorical, it's detrimental to the pacing of the game.

 

[Mad Vader]

You can say "big empires are unweildy", but the Roman empire was bigger than the USA for some 500 odd years, far longer than any country today, big or small, and for most of that period, open rebellions were very rare.

If you disregard local town riots or provincial rebellions and usurpers taking over a few provinces, sure, there were no rebellions at all!
Otherwise some would say that distance (or more precisely army reaction time) was the key factor in enabling rebellions, which doomed most large empires to disintegration by centrifugal forces.