
Nice visual image!
Originally, Morrus started up EN World to provide a place for campaign material (if I recall correctly), and for users of Eric's site to have a place to play. When Eric decided to shut down his Rumors and News site, he agreed to coordinate with Morrus toward a continuity of experience, whereby users of Eric's site could have the same account name (and stats?) on Morrus' site.
As for me, I joined when 4E was nearly beginning, because EN World had effectively become a Rumors and News site again, but this time for the fourth edition. I wanted a forum site I could use without having to rely on USENET; Google showed me EN World, and I liked it enough to stay.