They may have been expecting the people to throw human junk food out the windows.
That was my first thought. Someone may have conditioned these wolves to expect food from cars and humans.
I was on Assateague once, when a bunch of the feral horses surrounded our car, stuck their heads in the windows, sniffing us out. We had to just sit there until they realized there was no food forthcoming, and moved away.
Far more likely they were hoping someone got out so they could grab dinner and run.