The Medes were converted to Israelite religion by the deported Israelites from the Northern Kingdom of Israel and the Medes thus became Israelites themselves. The Israelite Levites were absorbed into the Median priestly tribe. The Israelite kohanim became the priestly caste of the Medes.
Alevis are descended from Israelite Levites and the Median priestly tribe. Bektashis are the non-Levite ordinary people of Alevi-Bektashi Judaism. There are Bektashis in Turkey west of Kurdistan, in Iraq south of Kurdistan and even in Iran east of Kurdistan but strangely there are no Bektashis in Kurdistan itself. While religious persecution could account for the disappearance of Bektashism from Kurdistan, this does not seem likely as much of Kurdistan remained Alevi. One explanation is that the Bektashis of Kurdistan were absorbed into Alevism. This could possibly explain why Alevis constitute such a large percentage of the population of Turkish Kurdistan. When this happened – if it happened – is furthermore unclear.