I wasn't there for DeS, but i guess it was filled up very much slowly. I think that people prefer play the game than spend their time for the wiki. But I also think that everybody is welcome to help fill it
Exactly right. The wiki can only fill up when people have really played the game. I have found things in the strategy guide that are not quite accurate as well, but this could only be found out by playing. It is very much a work in progress ALWAYS. Even the DS wiki has never been really completed since some things are constantly being found out that are different from what someone else has written there.
The wiki is a community project. Stooge and Ilkar created the guidebook that came with the EU version of Demon's Souls and Stooge was quick to point out that it wasn't just their creation, but that everyone that contributed to the wiki had a part in it.
If you take for instance one seemingly simple thing-how to kill the Hellkite (red) dragon on the bridge above the rats you will see there have already been many edits, simply because some tactics were not working for some people because he became invisible. It takes time to discover and verify the information that is put there and then someone can come along and completely rewrite what has been written which means someone might have to go back and fix it.
Also, it is a very large undertaking. Demon's Souls was big, huge. This is bound to be even bigger since the game is.