According to the article, they dumped her, because they didn't have the time for her. But it said it was amicable, so I didn't think it meant they had a problem with her or vice versa.
I think it makes sense to look at who she hired to replace them, but it doesn't make sense to interpret their leaving as part of a plan, unless you find some other article that suggests that she initiated it.
Yes, I noticed that too. However, being as far removed from the facts as we are, other inferences are possible. What if the reason they "don't have time" for her is A) because she was ramping up her demand for their time and they decided it was more than they could handle, or B) they just don't want to look like they've been fired, because that's bad for business. Until we hear Palin's side of the story, unfiltered, we won't really know.