Dragons are universally claimed to have been observed in cultures around the world. Keep in mind that despite embellishments and tales, there are consistent accounts around the world that show nothing more than seeing a dinosaur-type of creature.
There are a lot of stories people have told in the past, some are even told today. UFOs, Bigfoot/Yeti, Loch Ness, magical crystal powers, milk-drinking cow statues, ad infinitum. All have many 'witnesses.' Does that mean all stories, however fanciful, now and in the past are true?
Where is the physical evidence of all these 'San Antonio dinosaurs?' Is bigfoot intentionally hiding the evidence with the conivance of his buddy the Abonimable Snowman? Froissart is considered far more reputable a historian than Geoffrey of Monmouth, yet he had tales of some count turning into a bear at will, supposedly collaborated by witnesses. Because he said it does that mean you believe it? Was the plague caused by evil vapors? Are there four elements? Is the earth really flat? Numerically a lot more authorities than dragon witnesses said such was true.
That is until some people discovered science and demanded physical evidence of such wild assertions.
I think you may benefit from a good application of leeches to cure you of such melancholy vapors that seem to cause a belief in magical dragons.