This may be controversial but it's what I think.
In 'big' multisphere games and assuming everyone is reasonably sane and well mannered the effect of the initial staffing team, perhaps even the staffing team at any given time is important but not crucial. What's more critical is how well the overall project is accepted by and embraced by the community at large (which to be fair the names do play a very important role).
What I mean is, the scale of a large MU* like this is considerable - it needs players manning the political scene, populating coteries and packs, running plot, doing things. So a primary consideration is... do the people involved have the street cred (ahem) to generate enough interest and word of mouth to get people to go over and give it an extended try?
Momentum is critical in these endeavors, far more so than in smaller niche games, and the risk is inherently increased compared to a smaller scope since the playerbase is spread out thinner among all the spheres; if you roll a Vampire and look around to find a deserted wasteland of a sphere you are likely to move on, and so will the person rolling the next day since you won't be around to play with them. On top of that MUSHers tend to be very conservative, they'll sit on their current dying game they're actively bitching about rather than give another prospect a chance... unless it gets a good reputation right around then it's the Next Big Thing in which case players do turn to show up in droves - and then the challenge is keeping them.
For this having well known folks around headlining the project is quite important. It's far harder to pull this off as an untried newcomer no one has heard of even assuming they have the skill - obviously the game itself has to still be high quality, the grid and the metaplot must be well done, but to take advantage of it you do want players to show up in the first place.
That's without counting whether or not you'll get those rare players who'll lead in-game factions and attract others around them to generate roleplay. That's even harder.