Link to 2 million? I saw where they were able to datamine that it sold 500k in the first few days. That's a big jump to 2 million.
Seems it's just an estimate, Steamspy Premium estimates 2,376,000 as of 13th August.
It was the best selling steam launch of 2018.
It's highest peak concurrent players is 329k, which is the 6th highest peaking game. Behind only GTA5, PUBG, DOTA 2, Counter Strike and Fallout 4.
I'd say ~2m seems right.