Because that is how the whole Warcraft lore have always worked.
In The first game, Warcraft: Orc and Human, there is only Orc and Human. No old god, night elf, or most of race or lore, not even hints. In Warcraft 3, was the first time old god, panadren, etc. are hinted at. Then in WoW, Old god become the biggest bad guys. There is really no difference in how most of the titan lore, Old god, are introduced compare to Panadren. There was only vague hints and only starting at Warcraft 3. At least, a Panadren was in the game and actually played a part in the Founding of Durotar.
Still better than some race/lore in previous expansion or classic that is pull out of thin air.