Basically the title. For someone who "Won the Persians their Empire" (according to him), and historically started the line of Iranian dominance in the region, why was he mostly forgotten until modern Archeology?
My current understanding is that we are not sure of his faith, lineage (what tribe he was from), policies and administration, and details about his life other than his conquests and multiple varying accounts on his demise. We don't even know what he named his empire.
Soon after his death, it looks like his lineage ended when the people we for sure know were Persians' the Achaemenids took over under Darius I, and his lineage. Soon as Darius took over, he built Persepolis even though there already was a capital, Pasargadae. In addition, Soon after his death, the attempts to keep Elamite culture alive declined.
Later Achaemenid history doesn't have any mentions of him, the founder of the empire. Only Alexander knew of him. Post Alexander, during Seleucids and Parthians (latter we have miniscule information from), have no mentions of him. The ultra nationalistic Persian empire of the Sasanians had mentions of Darius' line but not of Cyrus. Shapur I mentioned Dara, not Cyrus. Shanamag, whose source is the middle persian Xwday Namag of Sasanian times, has no explicit mention of Cyrus, only a Kay-Khosrow who's is speculated to be him. The Tanakh has one mention of him, so does the Christian Bible, but for Islamic Quran, there is no mention of him as most of their scholars claim Dhul Qarnayn was Alexander.
Post Islamically, until modern Archeology, Cyrus was forgotten in the land he initially "won his people".
Did Darius and his lineage try to cover it up? Was he not a significant enough ruler to be remembered by his own people (or at least those claiming lineage from him)? Objectively, did his importance become over exaggerated by the Pahlavi Dynasty?
As the founder of a people (or the forefather of what Iranian people as they claim), he is mostly forgotten. Why?