IIRC, in the Vinaya, monks are restricted on the number of lower-ranked monks they can lead by a) their ability to effectively instruct and b) by seniority, which is measured not in terms of skill, but by length of time in the community. I'd have to look it up again to be more precise, tho. There was also something about their ability to provide robes and other requisites.
He was consulted as a respected authority, a senior member of the community