Why did Bukhari and Muslim not mention the Mahdi, and does that indicate that he is a myth with no basis, originating from Satan?

The hadiths about the المهدي are authentically established through successive narrations (mutawatir), and it is a firm belief. Some hadiths in Sahih al-Bukhari and Sahih Muslim refer to the المهدي without explicitly mentioning his name, among them the hadith about the descent of the son of Mary and his leadership of the Muslims, and the hadith about Jesus' (peace be upon him) leadership of the Muslims. The absence of a hadith in the Two Sahihs does not indicate its weakness, as neither Bukhari nor Muslim committed to narrating every authentic hadith.