Most mature oaks were just singed. Oaks have a thick bark which greatly increases survival for the core trunk. Surviving oaks sprout from branches and stems after a fire. Beetles are attracted to oaks after a fire. Birds and animals eat the beetles.
Fires prune the trees, kill the population of pests and rid the trees of the parasitic mistletoe.
Because of the natural processes at work, oaks can take hundreds of years to die. Most have deep roots which enable them to survive the long, dry summers. These deep roots are spared the effects of the fire. Just an inch of soil will protect the underground structure of plants. The crown root is a food mass which is filled with starch.