Red bull was never a major sponsor in my eyes. They tried their hand at a race team and they sucked. They're better at European style racing. Or were. They aren't so hot in formula 1 right now either.
Home depot is getting out because of a change in their marketing management.
Dewalt is still in the sport. Sponsoring Kenseth for 6 races this year. Had been with Marcos Ambrose for a few years before that.
Title sponsors change for all kinds of sports all the time. That's what happens with contracts. Sprint is a sinking ship so I can understand why they aren't re-uping.
But look at the sponsors that have been on cars or decades and haven't left: Axalta (formerly DuPont's coatings division), Lowe's, Budweiser, Miller, Catepillar, Bass Pro, Coca-cola, Pepsi, Mobil 1, M&M's (Mars Candy), Interstate Batteries, Menard's, and many others I'm sure I'm forgetting.
Yes they have jerked around with the Chase very often the past few years. But if you watched the broadcast Sunday, even the old guard say that it's the best thing that NASCAR has ever done. They change it because they listen to the fans and drivers. The way it's set up now rewards winning. I think the current Chase configuration will be around for a long long time. It makes the most sense.