Incorrect it dropped because multiple countries, whose oil production was minimal to none since the beginning of the Afgan/Iraqi wars, have started to increase prduction back to their previous levels. Couple this with the US raising their 40 year ban in oil exporting and we create the Oil Glut today. Obama's deal with Iran further exacerbated the issue as the Iranian's are ramping up faster then many thought possible. 

The Saudi's did however underestimated their keeping the market stagnant and the fallout it would have among the oil dependent Opec nations. More then likely OPEC's days are numbered, which is good. Its about time a more sensible group came about. Oil Prices should stay around 60-80 dollars a barrel, no more and no less. At that it would ensure continued growth, sustainable jobs and improvements in the energy sector.