Delusion is the right word, I would encourage people to read the whole Wikipedia. Despite his complete lack of academic training or ability (he failed the entrance exam to a military academy), he published several anthropological/archaeological books about Persia which were universally torn apart by actual experts. Two of them were focused on translating ancient cuneiform, but again, he didn't speak Persian, and "he failed to understand linguistic change and that Old Persian was not the same language as modern Persian."

Some of the cuneiform he "translated" was not even Persian, and he also used ancient mythical poetry as a factual historical source, claiming that ancient Aryans had conquered a race of giants. It's too much to quote here but it's all pretty funny: https://en.wikipedia.org/wiki/Arthur_de_Gobineau#Criticism_o....

Sidenote unrelated to Persia: He was so racist that when American racists translated his work (looking for justification to subjugate black people), they had to take out his rants about how impure American white people were.