until reykjavik, valorant was the most popular FPS in only NA. other regions were still playing mostly cs. and since reykjavik, it started getting more popular in other regions. and since other regions have more raw talent in FPS than NA does (lets be real, it's always been like that), other regions started to add strategies to their raw talent. that's why NA is falling down after their run through reykjavik and berlin.
thats my guess