This kind of a setup of a large number of small, cheap detectors works well for observing diffuse objects with low surface brightness. Generally speaking telescopes improve with size because larger telescopes can resolve smaller objects, so you can concentrate the light from your source into a smaller patch and increase the signal-to-noise with respect to the background. But once you have resolved the object (which doesn't require a very large diameter for a diffuse object) you no longer get any benefit from a larger telescope except for the greater light collecting power. So there's no benefit to having a single large mirror vs a large number of smaller detectors. Since it's a lot easier and cheaper to just buy a bunch of off the shelf components rather than build a large mirror from scratch that is what they did here.
A friend of mine in grad school worked on a project that is similar in spirit called ASAS-SN. It also used off the shelf cameras but distributed them around the world so that they could detect supernovae and other transients. Because everything was off the shelf they could build out their network on a shoestring budget. I think they're the first to discover the vast majority of all bright supernovae these days.