The business model has 2 components:
1. As they are one of the largest DNN vendors, they benefit from a larger DNN footprint. All content management systems have suffered from decline the last 10 years exept from the Sitebuilders (the Weeblies you mentioned). So, if they succeed in getting more people to use DNN, they are bound to sell more modules, themes and services.
2. The other reason why the Sitebuilders are popular is the easy start. Next-next-finish, no upgrade worries, it just works. Of course, you have less freedom but also less fuss. The business model here is https://www.vanjaro.com/pricing