This will start out with the same answer to this similar question:
"It is easy to stop a rubber ball than a wooden ball of same size moving with the same speed. Expain?"
But there is more ...
In addition to the great increase in momentum of the car compared to the bicycle, there is the relative difference in propulsion of each vehicle.
When an attempt is made to stop the bike, the propulsion device - the bicycle rider - will stop exerting forward force through the peddles almost immediately on braking or impact with an object.
When an attempt is made to stop the car its greater momentum is the dominant factor. But the engine in the car is also a factor because it has its own momentum in addition to the forward energy of the car. This energy will also need to be dissipated through the transmission, wheels, and tires to the road in the event of braking or impact.