Who (really) believes in God

I find these statistics very mysterious. Ignoring Bosnia which is a special case from which few inferences can be drawn, all 50%+ countries are non-Slav Eastern-Rite, all 25-50% countries are Slav Byzantine and all 25%- countries are Latin. What is the explanation? It can’t just be Vatican II because that doesn’t explain the inferior performance of the Slav Byzantines compared to the Non-Slav Easterners .