Distance. Loyalty pressure only goes 9 tiles. 1 city in range but it’s not enough to flip it Puel Mapu is 10 tiles away so not enough strength. You can get some idea of loyalty spread for the city by clicking on their emblem which gives a small loyalty line which you can then expand.
Then you can see the oppositions loyaly, here I can see I only have really to get 1 more pop in one of my cities to start flipping Chengdu, at least thats how I currently understand it.
If you look at the pop pressures in the city Chendu is currently only getting +0.3. Interestingly Wuhan is also getting pressure from my cities because it should be at +209 but is only +17.8. One city to the left and I would just fliup them I imagine.
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