They became a successful company by producing amazing games. Games like Warcraft 1, 2, & 3, Starcraft, Diablo 1 & 2 were straight-up fantastic games. The fact that they borrowed heavily from existing fantasy art and literature does not have anything to do with their gameplay merits. Fantasy is a genre that is always borrowing heavily from previous material. Did Warhammer invent Orcs and Dwarves?

To your second point: I agree. They’re not at all the same company that they once were.