The aim of the game is to get to the finish line as fast as you can, but that doesn’t mean that you are excuse from crashing the truck. Even if the terrain is very rough, crashing the truck is inexcusable and should not be done since it means death for the driver in real life.
Drive and climb as fast as you can to the summit before time expires. That is the whole idea of the game. You need to climb the summit in order to finish the level, but you also need to observe all the necessary precaution while driving a monster truck.