I quit watching mostly when 5 car stables (Hendrick racing) ,or 3-4 team stables (Rousch) would gang up, share technology, and dominate the sport. Small two man, or single (extinct)racing teams Nascar was built on do not stand a chance. Most fans who stopped going /watching did so when Jimmy Johnson won like 5 straight. He would get caught cheating at least once a year, slap on the wrist (can't piss Lowe's off). That and corporate sponsorship got more important than driver personalities. That is the reason NASCAR lost a fan base. part of it can be blamed on getting cocky and raising prices (supply and demand), but this was the wrong sport to try that on, and of course adding the cookie cutter mile and a half tracks (Chicago, KC, Phoenix, KY, Texas).
The 2,18,4 (Kevin Harvick), and a few other drivers tried to bring rivals back, but too many clean cut guys wearing all of those damn sponsor patches and when a mic is put in their face, no cussing or bad mouthing a guy, it was "I would like to thank the Lowe's, Coca Cola, Planters, Tampax, Viagra, blah ,blah, blah, Chevrolet it was a great car, but I got spun out and crashed etc etc etc.