Diablo Immortal earned $800k in its first 24 hours.
Until it doesn't. We're not talking about the same thing here because one is a one-time payment (license) vs on-going (loot boxes / SaaS). I'm highly critical of loot box (p2p) games, but you're on-going payments do pay for content in the future. Companies who charge once have very little incentive to maintain the software (assuming it requires it to).
Let's say ER reaches 20M + 8Mx2 for it's two upcoming DLCs @ $40 each. That's $1.8B lifetime. Pretty amazing! DI would need to make $360M per year to be an equivalent business. So 800k in the first 24 hours is not too far off track to being equivalent.