It was him hitting a car that started this whole scenario... but more to the point it was him fleeing the scene of that accident that started all this. Do I believe he purposely mowed down all those people? Well... yeah! I think the scenario is like BushMeister said...
It appears that this oldster panicked after the collision and said to himself "I'm in trouble now!" , and decided to flee the scene. He then crashed into the crowd and said to himself "Now I'm REALLY in trouble!", and kept his foot on the gas.
He was trying to get away... plain and simple.. and whilst in the act of trying to flee the scene he killed all those people. Your last example of an elderly driver losing control... smashing around all over the road... this aint what happened. The guy in this case made a bee-line straight through the market.. avoiding parked cars.. because he was trying to get away.