Responses
I don't think the author will choose to have Horus "stealing the sun's power" because it has already been shown in the story that many different Egyptian gods could and DID share the same domain: the Nile river, for example, is shared by Isis, Knum, and many other minor gods. Moreover, that wasn't how it went in the myth either (if anything, they had it that Horus "inherited" some of Ra's sun-related power, as her descendant/sucessor or whatever, and if anything, that the two of them "shared" that power, not that anyone stole it).
I'm pretty sure one of the hieroglyphs in the story said that Horus' intuition belonged to the sun. Maybe he stole some type of power from Ra and thats why he was murdered? But I'm pretty sure horus the elder was murdered by Seth, why would Seth care if horus stole from Ra?