The Ottoman Empire - The Great Revolt

The ottoman empire is this vast territory with presumably lots of resources, lots of man power. How are the greeks able to stand up to them? Why couldn't the ottoman rulers just crush this revolution? I think may be the central mystery of the whole thing. Almost everybody expected this revolt to be crushed like so many other revolts have been crushed beforehand. And i think it's hard for us to put ourselves in the minds of people in the early nineteenth century who believed that some spirit of the ancient greeks had come back to life.