Question: Why did the Sages not write a Megillah to commemorate the miracle of Chanukah, as was the case with the miracle of Purim?
Answer: A possible answer to your question is that the books of Tanach (Hebrew Bible) were written by prophets, all of whom were able to write with “Ruach HaKodesh” (Lit: “Holy Spirit,” that is, a certain level of prophecy). According to the Talmud, the ability to receive prophecy ended around the time of the destruction of the first Beis Hamikdash (Temple in Jerusalem). By the time the miracle of Chanukah occurred (2nd Century BCE), there were no more prophets left, and thus no one around who had the ability to write a book worthy of canonization in the Hebrew Bible.