no obstacle too great

The miracle of ner chanukah is that even though there was not enough oil for eight days, it was not an obstacle to lighting.  So too in our times, writes the Sefas Emes (5631), even though we don't have a beis ha'mikdash, even though we don't have the menorah of the mikdash, it's not an obstacle either.  The light that shines from our menorah is the light of that hadlakah in the mikdash. 

Putting aside the whole discussion of why you need a nes chanukah when tumah hutra / dechuya b'tzibur and the kohanim could have lit the menorah with tamei oil, the Sefas Emes (5641) asks a more basic question: Hashem could just as easily have made it possible to find eight jugs of tahor oil as one.  Even if you need shem zayis tahor to light, there didn't have to be a nes.

He answers that from the perspective of fulfilling the mitzvah of hadlakah, ain hachi nami, there didn't have to be a miracle. Hashem made a miracle not because hadlakas ha'menorah required it, but rather because we, the Jewish people, required it.  We needed a reminder that, "There are more things in heaven and earth, Horatio, than are dreamt of in your [Greek] philosophy."  A military victory is not enough to establish that, nor is political and religious control of the mikdash enough; there has a to be change in mindset, an acceptance that what teva says is possible or impossible is not the final word on the matter, at least not for us.  We needed a miracle to remind us of that.