The short answer is that we basically know a ton of people both in financial technology and in the valley. If people know you, know you're a good person, and know you're looking for something specific they'll often help you.
Tons of people have been surprised by our success to be honest. We had a talk with a potential investor recently and we told him who we were working with at [big bank]. The potential investor was shocked - the gentlemen leading our project at [big bank] is in charge of a 10-digit-a-year business and is a hard man to find time with. But one of our lawyers, who is also an investor, introduced us. They are old friends. Banking innovation / payments / technology, etc, is a small world.