Articles about Gygax and Arneson about their early home games that lead to the first published version of D&D.D&D was first published formally in 1974 so what "roots" were they returning to? Those WERE the roots.
If you read through thee there seems to be almost only hack&slash dungeon crawling going on. Characters were as nuanced as being named "Erac's Cousin" with such deep character traits like"dual-wielding vorpal swords". Or the great "Melf" who came to be due to the player not bothering with actually thinking of a name and thus "Gender: M" and "Race: Elf" combined into the famous wizard we know today.
Sessions seem to have most started right in the dungeon with no other motivation for being there other than the out of game knowledge that the DM has just invented something new and the players wanting to find out what it was.
Yet WoW merely shifted the "always evil savage" race trope from Orcs and Trolls to Gnolls, Murlocs, Centaurs and other NPC races existing only to be slaughtered.Whether or not they were first, I think you're going to be very hard pressed to say that WoW and W3 didn't do a lot of heavy lifting at rehabilitating the orc image for mainstream audiences.
And whenever an expansion needs an evil faction doing bad stuff, it's always the Horde that is lead astray, again, by an evil warchief