Sales of oil may not directly be a huge part of Dubai’s GDP right now but their economy is certainly very dependent on oil wealth in the region. The main reason why international companies would want to set up financial centers and have a local presence there is to take advantage of the oil wealth in the neighborhood.
They’re part of the UAE, after all, and just a 1.5 hour drive away from Abu Dhabi which is extremely reliant on oil for its economy.
