A few years ago, I heard a theory that Starcraft was created because GW and Blizzard could not finalise a deal on the latter creating a WH40K game. And as development was already in progress, Blizzard decided to create their own universe. Not sure if this is a telltale, or something more sensible.
Close yeah, though if memory serves it was Warcraft that came from a no-deal WHFB RTS pitch, Star Craft was the logical follow up in the 40K vein.