It's all about the timing of when Animated first came out. This was at that point when Hasbro was pulling inspiration from everything that had come before in order to create one single unified vision for the brand going forward. Had Sentinel been Rodimus instead, Rodimus being an unrepentive jerk that everyone is supposed to hate could have become his main thing for at least the next several years, with things like DOTM and TF One possibly even using him, instead of Sentinel, as their respective main antagonists, all because of Animated.Massively disagree. Animated Sentinel was a fun jerk. If that had been Rodimus I can see people getting annoyed at first before coming around on him as the series went along. Like they did with Sentinel.
Edit: ninja'd