Why they make a division like that? They wanted to reboot the franchise?
It's sillier than that. When they had the legal showdown with Chapterhouse a few years back (and were looking for a precedent that would make aftermarket car modifications illegal) they managed to put a whole lot of their IP somewhat stupidly on the line, and were told that they couldn't trademark generic words.
This is why they have in all their official stuff stopped selling Space Marines and started selling Adeptus Astartes and now Primaris Marines. They don't sell Eldar any more but Aeldari. But it wasn't half as easy to save Elves, Dwarves, Orcs, The Empire, et. al. from being considered generic words and they basically needed to nuke the setting and e.g. replace dwarves with Fyreslayers.
One of the most amazing things I've ever seen is that the people who did the Total War: Warhammer games pretty much precisely nailed exactly how all the voices were done by people back in say, 1991 (many but not all other Warhammer video games with voices have done a good job here - Fantasy tends to do better than 40K).
I thought when I played the original Shogun Total War that it was put together by either WFB fans or WFB would-be fans who found it too long to set up a game, and Creative Assembly is a British company. I'd be surprised if some of them weren't kids in GW stores in the early 90s.