The only 'fact' in this clip is that BG3 was 'outside the top 75 just a few weeks ago' while it is number 4 currently. The Steam page shows the game as having moved up 70 (with 29 weeks in the top 100).
This page shows BG3 at number 7 having moved up 20 places from last week. If I'm reading this correctly this is the US charts.
https://store.steampowered.com/charts/topselling/USAs somebody has already stated, one would expect a flurry of sales after three major video release a few weeks before launch.
EDIT: On the global sales chart BG3 is number 8, up 17 places after 16 weeks in the top 100.