The Talmud poses the question of whether the main mitzvah of Chanukah candles is the lighting (hadlakah), which would require all necessary conditions to be in place before that lighting, or the placement (hanachah) which would allow the candles to be lit in an inappropriate place, provided they are subsequently moved to an appropriate place. The conclusion that hadlakah is actually the mitzvah is recorded in the Shulchan Arukh (O.C. 673:2).

The Minchat Chinukh (98) notes that the Rambam (Hil. haBiat Mikdash, 9:7) writes that the lights of the menorah of the Beit HaMikdash could be lit by a non-Kohen, as long as they were prepared and set in place by a Kohen. (The Ra’avad argues that this is not permitted but merely acceptable after the fact.) Thus, the mitzvah of lighting in the Beit HaMikdash was defined by hanachah; as the Chanukah menorah is patterned after the Beit HaMikdash menorah, this is difficult to understand.

R. Chaim Brisker (Chiddushim to the Rambam) explains that the difference is rooted in the fact that the mitzvah of the Beit HaMikdash menorah was that the flames should be constantly lit. Thus, it is the presence of lit flames that constitutes the mitzvah, and, by definition, the lighting of the flames was merely a preparation for the mitzvah and not the mitzvah itself (see also Mishnat Ya’avetz, O.C. 75).