Guys only racing in their one chosen series is a comparatively new thing in racing. In the 1960s, Mario Andretti was racing in Indycars, Nascar, Formula 1, sportscars (in Europe and in the Can-Am series), IROC, and dirt track stuff like this all at the same time. So was AJ Foyt, minus the F1. Mark Donohue and Dan Gurney were all doing every series that had a warm seat for them too. That continued on for years, probably until the mid-80s until F1 and Indycar teams (and later NASCAR teams, once they got the top Northern talent) paid guys enough to tell them not to race elsewhere*.
I don't know if Stewart's consciously aping this tradition (although I'm sure he's aware of it) but given his co-owner status and pull as a three-time champion, there's not a lot of people who can say no to him if he wants to whip it around a dirt track on a Friday night.
I don't know if Stewart's consciously aping this tradition (although I'm sure he's aware of it) but given his co-owner status and pull as a three-time champion, there's not a lot of people who can say no to him if he wants to whip it around a dirt track on a Friday night.