Here's why:
* Old English continued to be spoken: Old English remained the language of the common people for centuries after the Norman Conquest.
* Literary influence: Old English literature continued to be written and studied for a while.
* Evolution, not extinction: The Norman Conquest brought about the introduction of Norman French, which influenced and gradually blended with Old English, eventually leading to the development of Middle English.
Think of it as a gradual transition rather than a sudden stop. Old English didn't disappear overnight but evolved into the language we know today.