On Language Log, Mark Liberman writes:
For most Americans, hurtle is pronounced exactly the same way as hurdle. And hurdle, in addition to being commoner than hurtle (about 7.69 per million for the “hurdle” and “hurdles” in COCA, compared to 0.60 for “hurtle” and “hurtles”), has the advantage of referring to a concrete type of object and a specific associated action.
This creates the perfect situation for eggcorn creation: a relatively rare and somewhat archaic word that is pronounced in just the same way as another word that is much more common in everyday usage, and has a clear meaning that overlaps at least metaphorically with most examples of the more unusual word.
If you hurtle through or towards something, you don’t necessarily hurdle any obstacles — but if there were any obstacles in your way, you probably would hurdle them. And the idea of moving quickly without regard for obstacles is not a bad proxy for the usual uses of hurtle.