Maybe they just weren’t that good at their jobs. Maybe they didn’t like her and she got on their nerves. Or maybe Palin wasn’t that good at taking direction. If she was determined to do things her way was there all that much that the staff could do to stop her? Trying to destroy your own running mate is too over the top even for McCain. Palin was shaky and uncertain early on, so it wasn’t like McCain would have been jealous of her when the country was still trying to make up its mind about her.
In the abstract, your suggestions are plausible, yet they seem inadequate as explanations for how Palin was treated. On the other hand, McCain’s life was marked by episodes of carelessness, impulsivity, self-indulgence, and stupid misconduct. While wrecking your own VP running mate is over the top, it seems like something that McCain might do.