" I'm not sure what their business model is. To be seen, but not to be actually doing anything of substance? "
I don't really think they expect any significant number of converts to come from the carts. The old D to D work never got many, when you divide the number of hours by the number of new converts each year. And a lot of those "new" ones are kids born in getting baptized.
Both the old D to D work and the carts are designed merely to keep J.W's Busy Busy so that they feel as if they are doing something, and don't have any time to actually think about the totally evidence free nonsense they have bought in to.