"if we assume the investors in this business do perform due diligence, is there another possible explanation? "

Wrong. Investors decided that they can make money with a business with an obvious predatory business model. It might be good money - at least in the short run, in the long run you run out of stupid people as I have seen with other types of such businesses - yet it is a company with a terrible business model.

Yes, I have looked at the picture you provided.

Shame on you.