"the philosophy of 'people helping people' is one of great value."
It is better to have a thesis that is narrow, not broad and general like this one. Perhaps you could write:
The great value of the philosophy of 'people helping people' as it manifests in credit unions consists of _______, __________, and ___________. (this will make it substantial and complex)
Your writing is very good, so the thing to do is model your 5 paragraph essay after their 3 bullet points. For each bullet point, write a topic sentence, which will grow into a paragraph.
For the historical significance of this quote, you can look here to get started: en.wikipedia.org/wiki/Credit_union#History
It is not about the quote, but rather, about credit unions. It will work out well this way; they are asking about the philosophy that underlies credit unions, not an analysis of the actual quote.