Pick a documentary, any documentary which purports to show the history of the vampire in true life and fiction. Countess Elizabeth Bathory will be there. She didn't have fangs. No-one has ever suggested that she drank blood. But she's there anyway.
In many ways, she merely fills a gap. She saves documentary makers having to leap from Vlad the Impaler to the vampire reports coming out of Serbia in the 17th and 18th centuries. With Countess Bathory bloodying the 16th century, it can look like there's an unbroken line of vampiric ghastliness throughout.
But they all pick the same unfounded story. Blithely the figure is trotted out - 650 young, female virgins drained of blood to fill the Countess's bath. If dramatized, we now get a shot of an actress practically purring as she wipes the red stuff over her body. All that's missing is the rubber duck.
The scene is gory and repulsive enough to have made it into vampire fiction too. When the vampire Carmilla is discovered lying in a coffin half filled with blood, it is because Joseph Sheridan Le Fanu had been reading an account of Elizabeth Bathory. The real historical figure is as vampiric as it gets, without her actually being one of the Undead.
However, the court records of her trial demonstrate that it never happened. Which isn't to say that the reality wasn't just as terrible, but the whole basis for Bathory's inclusion in the vampire myth is unsound.
It's unclear why Turóczi felt the need to invent even more gruesome details. However, the context might be revealing. The Jesuit scholar made the claims in his Tragica Historia in 1729. At the time, the Catholic Habsburg Empire was trying hard to secure Hungary. It already had nominal control over the territory, but winning hearts, minds, souls and, above all, allegiance was proving much harder.
In 1715, the Habsburg King Charles III banned conversion to the Protestant faith throughout modern-day Hungary. Anyone wishing to hold a position of authority in the country had to be Catholic or convert to Catholicism. At the same time, a massive smear campaign against Protestantism was launched upon the country.
Though an historical figure, Countess Bathory had been a Protestant. Her crimes made her fair game for being paraded as an example of the worst excesses of her faith. But for this purpose it wasn't enough to describe her merely as a sadistic serial killer. As the descriptions grew more lurid, then it was supposed to point to the evil inherent in Protestantism.
In reality, all it did was create a vampire legend, which continues to be repeated to this day.