Until now we talked about sight as a differentiation but now we talk about sight as a commemoration. Recognizing the greatness of Hashem through a miracle that many or one experienced.
The Magen Avraham (686,5) says that people can make like a Purim a national or personal holiday to commemorate a miracle that happened on a particular day. We are not diminishing by this the importance of other days. We don’t mix one enjoyment with another not to diminish from each other. The Chasam Sofer in Maseches Shabbos (22,1) starting Pesulah, says that there is a biblical mitzva to commemorate a miracle that happened to one from a kal vochomer, if servitude to freedom praise required certainly from death to life. Therefore the Behag holds that Chanukah and Purim are biblical but the method of commemoration whether throgh lighting candles or reading of the megilla, as the neis happened through the king not being able to sleep and reading a megilla, is rabbinical.
I one heard, יודו לה’ חסדו ונפלאותיו לבני אדם when we get cured we should thank Hashem who healed us but we see the wonder in the doctor, a human being. That is why we don’t find Moshe Rabbenu being praised in the Haggadah as he is a tool of doctor, Hashem. The Midrash asks on ויאמינו בה’ ובמשה עבדו – אם במשה האמינו בה’ לא כל שכן if they believed in Moshe than certainly they believed in Hashem? אם כן למה נאמר ובמשה עבדו so why does it say in His servant Moshe, to teach us whoever beliefs in the talmid beliefs in the Rav. The question is, it should have said, why does it say they believed in Hashem? Maybe, since all the abilities of Moshe Rabbenu came from Hashem it is obvious that if they believed in Hashem than they would also believe in Moshe Rabbenu as Shimon Hamosini did not need to learn to fear talmidei chachomim as their abilities come from Hashem whereas Rebbi Akiva was am haaretz, so for him that was not so obvious.,