I don't know, I think it's all about MDI (Mythic + dungeons) and AWC (arenas) nowadays and both these scenes mostly have the same ~300 people involved in tournaments for years now. It's a tightly closed gated community. Most of them are streamers, they bring visibility but based on
Esports teams & tournaments stats: Dota 2, LoL, CS:GO, HS, Fortnite, PUBG viewers average 30k for MDI and 40 for AWC.
It's good but the production is minimal with the same 3-6 casters and Blizzard as always isn't doing a great job featuring them. Also there's no merch market for the average player, arenas are very difficult to get into and MDI is mostly about which team is gonna wipe first.
Seeing how much Overwatch franchise fees cost, I bet they make more money selling OWL spots for $20-50m each with minimal production. OW World Cup where teams aren't paid -though flying World Cup people to Anaheim once a year does cost them money indeed- but it's a low effort and Overwatch overall viewer rating is sinking for months now.
What would make them money is how new people get attracted watching MDI/AWC get attracted to WoW. Surely there's people out there watching arenas or M+ thinking "I'mma play that'" but I don't have the knowledge to number that. Also WoW and esport never really got to the place the most played MMO of the latest 20 years should be. Earlier this year, the Activision Blizzard layoffs reporterly hit most of the production teams, lots of them supporting esport. It's not a good sign when
in charge of esport leave the company.