I am pretty sure lots of maniacs throughout history tried drinking blood. They must have inspired the vampire myths but I don't think they flew, recoiled at the sight of cross or pulverized on exposure to sunlight.
As for Dracula, he is a fictional character based on a real person. Sometime in 15th or 16th century, a man called Dracul ruled present Romania. He was basically a medieval despot plus he was a psycho. He killed people in gruesome ways like putting them on poles alive. He probably did eat the flesh of his vanquished enemies and drank their blood. In 19th century a British author made him into a novel character, hence was born Dracula the vampire.