The Challenger doesn't crash...
Just watched the ending of the movie again and remembered a discussion from the past.
The car that crashes into the bulldozers is a Camaro, not the Challenger Kowalski was driving. The side and rear end of the car crashing into the bulldozers is a Camaro (said to be a 1969), evidenced by the different profile and tail-lights. Later, when the fire is extinguished and people are going through the wreckage, there's a ~1 second pan shot that clearly shows the Camero emblem.
Speculation is that Kowalski either veered off at the last second, leaving another car (a Camaro to crash) or simply vanished (having reached the "vanishing point" of his sanity and existence).
Of course, the real world answer is that the director never expected anyone would notice the car switch with the frame by frame analysis capability of modern video.