Having only one basically lawless land was a factor but the real reason they were losing large amounts of players was the fact that they were no longer the only game in town. Plain and simple.It wasn't just because people were whining. They were losing subscriptions over it, and by the tens of thousands. Both RB and Kosner have both said the same thing. And the guy there gives out numbers. Trammel effectively doubled their subscription base. Who knows how large it would have been if Trammel (or something similar) had been done sooner.
You can dissect it anyway you like but that is it in a nutshell.
Online gamers are without a doubt a fickle bunch and always want the latest and greatest. That was true then and it is ofc true now.
And you cannot try to compare sub numbers with current popular games that sustained a longer growth period simply because the entire genre itself has exploded
UO was created and thrived in a wild west atmosphere. That same atmosphere was not its downfall a few years later.