val has more currently active players than csgo, but csgo (i would assume) has more total players (as in, people who have played in the past but might not necessarily play any more).
generally a game (esports or conventional sports) tends to be more interesting to watch if you've played it yourself and understand some of the details. so i feel like just taking active playerbase as a metric is a bit sketchy.
additionally, cs has been around much longer as an esport. it takes time to accumulate a loyal viewerbase. up until now, val hasn't even had a consistent format yet. i reckon the new league system, plus crowds at LANs, will probably do their part to help val gain more viewers.