The observations of the pacific cargo cults are an example of religious and cultural syncretism which took on many varied and unique forms most commonly with the sudden increased presence of colonial and military forces in the Pacific along the very varied cultures and groups in that area especially during and after WW2 (and their subsequent sudden departure).
But it is similarly a step too far to imply this phenomenon or the resulting cults that developed was deliberately cultivated by colonialists or that military presence.
The "cargo" elicited in the term cargo cults is directly tied to this phenomenon: WW2 saw suddenly huge amounts of goods and logistics suddenly appear and then disappear from the Pacific regions as the war was fought and then subsequently finished.
Now there are also examples of religious syncretism that forms from missionaries trying to introduce Christianity to places all over the world (see South American and African interpretations of Christianity blending with local traditions), but those are not the cargo cults referred to that explicitly capture the primarily WW2 Pacific phenomenon even though there are other examples of syncretism of Christianity and Pacific religion that aren't cargo cults and aren't deliberately cultivated. Indeed, many times I'm guessing some of these practices are explicitly meet with resistance and annoyance from the likes of colonial missionaries and authorities, so as with most things its not that simple.