I really don't think you're grasping what's happening here. This is not a new game. No development went into making it available on steam. When you open it in steam, it opens the battle.net launcher. It is literally the same game.

Imagine there's a food truck around your neighborhood that has given people food poisoning and is known for having poor quality. Now imagine they move the truck to an adjacent neighborhood. Does that change anything about it? Are people's complaints about the truck suddenly invalid? Should they just get over it and stop holding a grudge?