Monotheism

It's popular to say that Moses learned from Akhenaten (one of his poems resembles a psalm), and I've heard the reverse--that Akhenaten learned from the Jews. Given the difficulty with dating anything, I don't think that line of inquiry is very fruitful.

I like another approach. As I've read elsewhere, and Rodney Start reminded us, a "High God" tradition is pretty universal among "primitive" groups. In The Idea of the Holy Otto describes an "encouter with the numinous" that he, I think properly, regards as the source of religious feeling. Depending on when and where this encounter happened, you might attach the sense of awe with the ocean, or the stars, or the forest, and come to think of that as the god. The default numinous experience would be monotheist.

Polytheism comes in when the original experience fades, or you have to get along with (swear oaths for) neighbors who either had a different experience or inherited the rituals from someone who had a different experience. And henotheism devolves to polytheism (by the next generation, if not sooner) which will dilute devotion.

If this approach applies, then Akhenaten had such an experience, and was in a position to (at least for a while) defy politics and tradition and try to inspire everyone to give up the corrupt rituals of non-worship in favor of a truer devotion.

In other words, the two could have been indendent.