Royce and Ken Sham got the sport off the ground, then you have other inflection points like the Griffin/Bonnar fight. Fighters like GSP and Brock helped grow the sport a lot.
But much as I hate to say it, it is ridiculous to say anything but Conor if you are talking growing the sport commercially. No one else is close.
As far as promotion, Dana and Zuffa really brought the sport to a larger audience back when Dana wasn't a total douche.