@Metla
Assetto Corsa have 1997 players/month total-you can see this in op post. And noone can say if most of em playing online or offline. I assume offline. Iracing had 70000 players in the beginning of 2018 (i found this info using google). This means at list you will find online races faster in iracing than in AC.
Twitch= more viewership=> more potential owners.
So no. AC is not even close to Iracing. Also from my experience game with less than a 5000 online players=dead game. I am playing fighting games from time to time (1vs 1 pvp) and if game goes below 5000 you will loose 15-30 mins waiting for random fight,and also you will fight vs 2-3 same persons.