I was also surprised by that sponsorship. While cs2 is not that popular to the gambling community, sponsporing the #1 team will add huge exposure to Stake's gambling platform.
actually, gambling is huge in counter strike. almost every tier 1 team is/has been sponsored by a gambling site, especially skin gambling websites.
but nothing as big and mainstream as Stake, which is why it's a crazy sponsorship for the cs2 scene.