In this kind of scheme, earlier investors are rewarded with the money from later ones, making it appear like what they are investing in is a success and therefore encouraging others to participate.
A few more minutes into the movie we get introduced to the main protagonist in this story Gerry Cotten and learn that Cotton has become rich off Crypto and has started his own exchange which takes bitcoin and converts it into Canadian Dollars.
In reality, Cotten spent, traded and used those assets at will.