I heard it was because Sega were very poor because they kept releasing shit consoles, but then they took out the Dreamcast (which was amazing), but they didn't market it correctly, resulting in death.
That's what I heard anyway.
BTW, OP and anyway else who has a Dreamcast HAS to buy Shenmue. You can't have a Dreamcast without Shenmue. Shenmue was the reason I brought another Dreamcast.
It's literally the best game ever created.