I don't take your biased attempts to undermine the popularity of plate racing seriously myself. It's way more accurate of having more entries than places for the Daytona 500. Nascar isn't kind to teams who don't have charters and have to run open cars also.I dunno if it's talent or interest. Many of the top Indy drivers will run as third and fourth drivers in the IMSA endurance events. Maybe most of them view sprints only as stepping stones, or maybe they just don't like that form of racing.
Speaking of forms of racing, I suspect the D500 being a pack race probably does more to deter outside drivers from entering than any other single factor, including the layout, expense, or overall talent level.