It's possible Adonalsium was not the god of the entire universe but just of a small section of it where Brandon's planets are. If we're thinking there are only 16 shards, and two of them ended up on the same planet (and Hoid is hopping between Shard worlds), it's possible the shards are spread over a relatively small astronomical area. If that's the case, it might be because that's the area that was Adonalsium's domain.
Going off that thought, Ookla, even if Adonalsium's domain was a single galaxy, that's still a vastly huge area compared to what we currently experience. And a single galaxy is
tiny compared with the universe. Adonalsium need not be God of the entire universe (as the universe is unfathomably vast), but could control a region so large from the perspective of a single planet, he may as well be considered
a God.
Also, there doesn't have to be just 16 Shards. I thought 16 was Preservation's number, not necessarily anything that we could apply to all Shards. Now, there
could be 16 Shards, but I don't know yet. We shall see.
I would think that Adonalsium would have a conscious aspect to it, considering how important a conscious aspect is to a Shard.