Being second to market has not hurt Apple in the past. The iPhone was not the first smartphone, and the iPad was not the first tablet, they just made both products much better that what existed in the marketplace at the time.
Car manufacturing is a cut-throat, low margin business and I don't think the projected returns were there for the finance guys to sign off on it.
Same reason they've never made a TV, despite years of speculation, there are already great TVs out there, and it's not a high margin business.
Apple also prides themselves on their ability to differentiate themselves from their competitors in their chosen markets, perhaps here that was not a possiblity either.