If I had to steelman it, perhaps groups constantly have to fight against the natural entropy of spending more and more on outreach and less and less on object-level work. And perhaps it is a train that once you start is hard to stop: if the movement builders are optimising for growth, then the new people they train will optimise for it as well and then there becomes an entrenched class of movement-builders whose livelihood depends on the spending continuing to remain and whose career prospects will be better if it further grows.
If I had to steelman it, perhaps groups constantly have to fight against the natural entropy of spending more and more on outreach and less and less on object-level work. And perhaps it is a train that once you start is hard to stop: if the movement builders are optimising for growth, then the new people they train will optimise for it as well and then there becomes an entrenched class of movement-builders whose livelihood depends on the spending continuing to remain and whose career prospects will be better if it further grows.