[chaosprime]

I'd say it's a little less about luck and a little more about effective evolution. A "successful" MUD that became that way without any sort of coherent design very likely got there, instead, by a series of many ad-hoc revisions that were successful at growing and retaining user base. The fact that these revisions achieved this effect isn't a matter of pure luck, but unintended consequences being what they are, it's not pure design either.

Now, the Venn diagram of "success at growing and retaining user base" and "pandering to the lowest common denominator" is left as an exercise for the interested student.