There are about 1.25 million Seven Mothers initiates in Glorantha. There’s probably another 330k Lunar initiates of other cults on top of that. That is one of the most successful new religious movement in Time!
In the lands where the Lunar Empire is active (Peloria, Dragon Pass, Holy Country, Maniria, and Prax), there about 740k Orlanth initiates. There’s another 400k initiates of the other Lightbringers (Chalana Arroy, Eurmal, Issaries, and Lhankor Mhy) in those areas. Beyond in Ralios there’s another 560k or so Orlanth initiates, and another big but unspecified number in Fronela.
Ernalda in those same core areas has another 960k initiates (not including Ralios or Fronela). The Grain Goddess cults add another 590k or so in those areas, and Dendara adds another 181k.
Meanwhile Yelm and his family add another 980k initiates, although well over half is just the Lodril cult. Yelmalio adds another 200k.
So when we think about these big groups of cults, it is obvious that both have broad appeal to large numbers of people, and in many areas they even overlap.