a non-supernatural Cassandra - a soothsayer (accurate forecaster, lie-detector and truth-teller) unable to get other people to pay attention to and care about the truth.

a previous Cassandra, Hanna Arendt:

Uncommon Sense: Totalitarianism

notes that it's a very widespread and endemic problem among humans - not just modern politics. It's the whole basis of religions too. The C of E has been infamous for its hierarchy not actually believing themselves but thinking it was important to get the peasants to play along.

was never fooled by the incredibly bad pantomime and has always struggled with being stuck on this planet with such an evil, incompetent, dishonest and gullible species running it.

Cassandra was the original Cassandra!

but possibly fictional (at at least pretending to be supernatural in her predictions).

definitely mythical. She was cursed by the gods to be always accurate in her predictions and never believed.

yes, it's only a question of whether any sort of real person lay behind the myth at all. A bit like the arguments over historical Jesus.

the stories of the Trojan War are so old there's no chance of a historical record.