I think it's possible to do that, but just don't expect the people on the other platforms to get excited about it. Using a phone as a primary gaming device is partially about mobility but mostly about budget (at least going by how I see it). Someone who already has a gaming PC or console doesn't really want mobile games. Personally, while I used to have more of a variety of games on my phone, currently my only game is chess, despite considering myself a big gamer.

Blizzard's mistake wasn't in making a mobile game, it was thinking they could excite a room full of PC gamers with news about a mobile version of a big PC game, showing just how out of touch their leadership was. Like it should have been obvious that that presentation wasn't going up be taken well and should have either just been a booth at blizzcon or an announcement that said "mobile game" right from the start. I forget where in the timeline that fell compared to their other blunders like WC3 reforged replacing the still superior WC3, but IMO it made those other ones more predictable because it was a clear sign their leadership was just chasing the money without a good idea of what gave them fans in the first place.

If xbox handles it better, it could work out better for them. Not for winning me as a customer, but for increasing users who do like to game on mobile environments.

Diablo Immortal was successful for blizzard on its own, though it's hard to quantify lost business because of it (especially when it wasn't the only thing hurting business for blizzard).