In short, the donations come from brands/corporations. The donations your nonprofit receives come directly from the ShoppingGives Foundation, a US-registered 501(c)(3), and are pledged by our brand partners.
ShoppingGives brand partners either directly selected your nonprofit to direct their generated donations to, or they give their customers the opportunity to select a cause they care about most to support with their donation. It's likely that most of these donations came from the customers, if there is no default cause set.