How authentic are todays Israelites. Are they really Abrahamic stock.?

Doesnt the bible say that when Israel was taken into captivity the king of Assyria brought people from Babylon, Hamatz, Serphavaim etc and settled them in Israel to replace the Israelites. When these people came to Israel they did not worship God and God sent Lions to kill them until one of the Israelite priests was sent back to Israel to teach them how to worship God (2 Kings 24).