Why did my back bike tire pop off and lock up and bend?

I bought a Marin Muirwoods 29er two days ago and I was going super fast down hill I probably hit thirty five forty mph and I heard a pop and all off a sudden i was fish tailing everywhere and skiing everywhere across a busy highway and when i finally came to a stop and ran back to pick up my bike the tire and back forks were mangled. The bike is designed to go fast so i don't understand why this would have happened. Luckily I didn't go down and avoided getting hit by the traffic around me cause i would have probably died especially not wearing a helmet. Anyone know why this would have happened?

the tire didnt pop

You should check your quick releases on your wheels every time before riding. My guess is that the rear QR was either engaged incorrectly or just barely enough to hold the wheel in place.

It may have also had a tire/tube defect, but since you said the tube didn't blow, well, that is ruled out. One other possibility- and you'd have to take it to the shop- is that there may have been a frame defect. This is VERY unlikely but I have seen it before. Hopefully you haven't taken the bike apart or the hopes of any warranty will be lost.

Maybe the inner tube had a piece caught under the edge of the outer rubber tire shell. The pressure caused the inner tube to puncture. Or you may have run over a sharp piece of glass or a nail. Was the rear quick release lever pushed down (attaching the rear wheel to the frame)?

be as the person who said ( I am not the stupid who buy the cheap twice)

cause yo bike sucks and is cheap