You want to let your players do the things that they think are cool, so I don't think you did anything wrong with how you adjudicated the destruction of the jeep. (As an aside, I agree that there should have been some equal and opposite force applied to the character though. I may have had them take stress equal to their roll, the strength bonus not included.) I think you could have salvaged the scene by not having everyone inside the jeep taken out though. The cool thing about being the GM is that you can adjust things on the fly if it will make the scene more fun. That includes changing powers and skill levels if the scene is not working out in an enjoyable way, or even swapping in different NPCs if they haven't been revealed yet.
In Fool Moon, Harry flips a van filled with the Street Wolves gang. Now Jim Butcher could have put anyone in that van, a mortal, a god, or the Street Wolves, but the most interesting thing to put inside was the Street Wolves because they could survive the crash and present Harry with a possibly beatable, follow-up challenge. Jim says that the most interesting answer to the question of whether or not your protagonist will succeed is either "Yes, but . . ." or "No, and furthermore . . .". Yes is boring, hence why you're here, and no is frustrating if overdone. So in your case, the answer should have been . . .
"Yes, you destroy the jeep, but you've taken a consequence from slamming your body into a jeep hard enough to knock it off the road, and the attackers inside survive to come an attack you."
Or
"Yes, you destroy the jeep, but inside was the son/daughter of a person that is scary and now really mad at your for hurting his/her progeny."
TLDR; I think you did fine, just work on your creative improvisation to make the outcome either a "Yes, you succeed, but . . ." or "No, you fail, and furthermore . . ."