The storming of the Bastille was caused by multiple reasons that were building up in the French society for some time. France was in a bad situation. The economy was in dire state, largely because of the bad policies and the French intervention in the United States. The aristocracy was acting terribly towards the ordinary people who were suffering and in the verge of survival.
After the initial few attempts failed to reason the king to make certain reforms and to improve the countries situation and the situation of the people in it, the French people decided that enough is enough and that they will take things into their own hands.
The medieval castle, also a prison, and a symbol of the aristocracy of France, Bastille, got broken into it by the people. They released the prisoners who were sentenced because of refusal to shoot at the citizens.
The ordinary people outnumber the aristocracy by far, as the aristocracy was only 2% of the population, so the people, united, managed to take down the king and the aristocracy with relative ease.
