Just had an achipelago game as polynesia where Attila flipped 2 cities to me, which rather confused me as in pangea or earth games I've had more tourism, culture and borders that actually connect, Attila was halfway across the map on huge, I had a small colony a bit closer to him, but there was an entire civ between us and the city was relatively new and low and culture and probably without any tourism, also interesting is that Attila didn't even pick an ideology yet, using polynesia's early sea faring shtick I managed to get some very strong production cities going and snipe most wonders after classical, but cities flipping halfway across the globe while neighbours are completely fine?
I get the impression distance is irrelevant and the only factor is the "defending" civ, as Attila's AI probably forgoes any culture for military, he probably had the lowest culture and tourism in that game (probably followed by Bismarck, but he was my best bud and adopted freedom relatively quickly after me, and despite being much closer nothing ever flipped.
Just realized I'd city state bribed freedom to be the world ideology, perhaps this is what triggered it while he lacked any ideology of his own?