Because CS:GO was broken in the best ways. It had "tick rate" debates that fueled a decade of forum wars (64 vs. 128). It had the $0.15 skin gambling economy that mimicked the Wall Street stock market. It had maps like Cache and Old Dust2 that had been polished by the tears of a million rage quits.
through the "Betas" tab in the CS2 properties menu on Steam, or via a standalone unlisted link if available. Interesting Review: "The Gaming Rorschach Test" Download Counter-Strike- Global Offensive