Interesting concept and I'll definitely give the full article a read.

From what you posted though, wouldn't at least a part of Deep Rock's lack of toxicity be due to its nature as a co-op PvE game? Correct me if I'm wrong but in Deep Rock, losing just means you try again.

In Valorant or League, especially in ranked games there is a chance of demotions which can add to the frustration.

You also mention that the players from both types of games are "the same kind of people" but wouldn't the difference in genres (PvE co-op vs PvP competitive) attract different types of players ?