...what I don't understand is that if Buddhism teaches that victory comes from being passive ...
Buddhism doesn't teach that.
It does teach some Yoda-like doctrines (or vice versa); for example if Yoda said ...
“Fear is the path to the dark side. Fear leads to anger. Anger leads to hate. Hate leads to suffering.”
... there are versions of Buddhism which might say something like (I paraphrase as follows),
Ignorance is the path to the dark side. Ignorance leads to greed. Greed leads to aversion and suffering.
Famous Buddhist doctrines include statements like,
Mind precedes all mental states. Mind is their chief; they are all mind-wrought. If with an impure mind a person speaks or acts suffering follows him like the wheel that follows the foot of the ox.
... and ...
Hatred is never appeased by hatred in this world. By non-hatred alone is hatred appeased. This is a law eternal.
Still, I do see the quote you're referring to, i.e. which says:
"That's a pretty radical idea," she said. "We're used to the hero fighting; slaying the dragon or killing the monster. That's what we find most familiar. This idea of triumphing by not fighting, of being passive, of letting this power work through you, is a very Zen type of idea."
I think my answer to that would be that Japanese "Zen Buddhism" comes from Chinese "Chan Buddhism" which includes Taoist influences.
Doing by not-doing is IMO more especially Taoist (than old-school Buddhist), where it's called Wu wei.
The literal meaning of wu wei is "without action", "without effort", or "without control", and is often included in the paradox wei wu wei: "action without action" or "effortless doing". The practice of wu wei and the efficacy of wei wu wei are fundamental tenets in Chinese thought and have been mostly emphasized by the Taoist school.
The concept of "effortless action" is a part of Taoist Internal martial arts such as T'ai chi ch'uan, Baguazhang and Xing Yi.
A Taoist martial art is not wholly to do with being "passive" though: e.g. it could be to do with being soft and hard, passive and active, empty and heavy, etc.; or using the opponent's weakness; or waiting until they attack first; etc.