I'll admit that I didn't read past the OP, so I apologize if I am restating anything.
I feel that one of the largest influences on dominate teams is the returning students. If a student that really helped the team one year returns after they graduate, I can see them doing well again. As knowledge gets past down and grows from year to you, you begin to realize that this is nothing like your typical sport. In football a player can not say "Hey, let me lend you my endurance," but in FIRST student can say "Hey, let me share my knowledge." It is that reason that dominate teams will most likely stay dominate.
Another reason is their connection. I feel pretty certain that strong teams make good connections. Not only with sponsors, but with other teams. Just look at 148 and 217. There are times when a team/business/person is only as good as their connections.
My $0.02, take it or leave it. (Feel free to throw it off a building after lighting it on fire. But if you do; I want a video.
)
-Rion