There are lots of factors that separate a successful payment method from an unsuccessful one. Ease of use, the right industry support, the buzz of social media, all play their part, but none are as important as trust.
Money itself is predicated on trust, it’s a promise. Take the common banknote, for example. It has no intrinsic value in itself; it is a form of negotiable instrument known as a promissory note whereby the bank will pay the value of the note if so demanded. Even the value of money itself is entirely abstract, it’s what you can do with the value that’s important, and everyone has to agree to participate in the same way for it to work.