I don't think that the number of people that are affected originally is not necessarily indicative of how meaningful it is. Sometimes something that begins small and maybe affects only a few people in the beginning can go on and affect so many more. I think writers and speakers have no idea of how much of an impact they can have on their readers and listeners. I am thinking of something like the Gettysburg Address where the actual live audience was not huge but for millions of people who have read it there is a huge influence.
I am going to post on Cake about a book I am reading as soon as I finish it. It is about a young Stanford Business School graduate who wants to help the poor in Africa. She writes about some of the failures of good hearted people and organizations and why they fail. And she writes about successes. Some of the successes seem small but can go on to affect generations of families as they rise out of poverty.