That was back when Apple was adamant not to use any fans whatsoever in their products. I remember it well. It was nice with the silence but limited the products in other ways. It really goes all the way back to the Apple ][ which had one of the first switching power supplies (runs cooler) but without a fan, which could lead to overheating, especially since it didn't have any other fan either and could be expanded with 8 internal cards which could draw a lot of power.The cube had massive cooling problems though...
The cube was to use convection cooling only, but that only goes so far.
Still, it was wonderful times with an innovative and playful Apple firing on all cylinders.