Because this is the religious map mode, the countries are still the same as 867 if I'm understanding correctly, which is why Greece and Anatolia quickly consolidated to Orthdoxy (whether they started as it or not I don't know, but they have a bias towards converting the state religion to Orthodoxy so that probably had an effect even if one emperor tried to make them Mutazili). I'd imagine that Catholicism did well as well because of crusades, which would be powerful when most of the crusade target's neighbors have no reason to help them (I mean why would an AI Zunist care if a Bönpo got attacked by an Ashari for example). Catholicism was also probably able to consolidate western Europe as the Apostolics controlled the Holy Land, and as Ecumenists they can't have crusades sent at them (usually).
And yet this is still not the most surprising religious map by the end of the game
I'm actually really impressed with how Catholicism managed to reassert itself in Western Europe given how it started out
Boring, it always ends with the same religions. Hellenism barely breathed.
Some religions are just coded to be superior in spreading like Islam, Christianity and Judaism
Why do they move like countries
Because this is the religious map mode, the countries are still the same as 867 if I'm understanding correctly, which is why Greece and Anatolia quickly consolidated to Orthdoxy (whether they started as it or not I don't know, but they have a bias towards converting the state religion to Orthodoxy so that probably had an effect even if one emperor tried to make them Mutazili). I'd imagine that Catholicism did well as well because of crusades, which would be powerful when most of the crusade target's neighbors have no reason to help them (I mean why would an AI Zunist care if a Bönpo got attacked by an Ashari for example). Catholicism was also probably able to consolidate western Europe as the Apostolics controlled the Holy Land, and as Ecumenists they can't have crusades sent at them (usually).