Complex sentence: FIFA ranking's use of regional multiplier is the primary reason why most teams in AFC and CONCACAF have significantly lower FIFA rankings compared to ELO rating based rankings, while the weaker teams in the UEFA have significantly higher FIFA rankings in comparison to ELO.
Split into simpler sentences: FIFA ranking's use of regional multiplier is the primary reason why most teams in AFC and CONCACAF have significantly lower FIFA rankings compared to ELO rating based rankings. Meanwhile, weaker teams in the UEFA greatly benefits from the FIFA ranking system and have significantly higher FIFA rankings in comparison to ELO.