Let's look at his San Andreas playthrough from 2018 where he muted the music.
Part 1 got 28k views to date.
afterwards, his views drop significally to around 5k per vid.
At around part 40 he barely breaks 3k per video. On some videos, he barely scratches 1k views.
The whole playthrough consisted of 178 10-15 minute long videos totaling 330k views.
Now, I don't know his CPM on the top of my head, but going with 3 CPM, this whole playthrough would've net him around 990$ in ad revenue.
Nowadays, he thankfully doesn't split his VOD's into 10 minute parts so this playthrough would be around 35 videos long.
Let's be generous and say he'll get around 2k per video. This would mean he would get around 70k views (or 210$) on this playthrough.
At this point, it is simply more profitable to leave the music on and beg/guilt trip his audience.