That's exactly what stifled their growth. What other Clans easily accomplished between their lower castes, the Mandrills made a struggle of due to inter-kindraa fighting and bickering. If one of the kindraa did get ahead with a scientific advance or a surplus of trade goods, the other kindraa would trial for it, or the first kindraa might refuse to share with certain other kinraas that they feel rivalry with, etc.
How they became as strong as they did by Operation Revival we may never know. The Mandrills had built up an impressive Touman, only to squander it through inter-kindraa fighting over every aspect of the invasion and the trials that led up to it.