Have to say, I, disagree with your two points.
Car culture is still alive and well, if anything it’s more saturated. How many car shows are on TV now? 3/4 Roadkill variants, multiple “customizing” ones ( some are complete garbage, like Texas metal ), numerous how to’s…Meacum and Barrett Jackson command whole afternoons dedicated to a show highlighting vehicles that most watching could only dream about buying.
When I was just a kid…glasspacks, air shocks, traction bars and a Holley DP. Then came the Fox body revolution….underdrive pulleys, Flowmasters, GT40 intakes ( yawn ). Now it’s tuners, turbos and fart cans.
Instead of Burt and Trans Ams, it’s Vin, a Mopar, and numerous imports.
NASCAR’s decline was largely due to, imo, over expansion and the Great Recession.