And from what I understood they only had concept art for Grievous to go off of, so they had to invent his personality on their own.

But to be fair, I understand why George wanted to make this General character a mustache-twirling villain that runs away and gets beat over and over. It fits into that villain archetype of old serials. I don’t think people would have been as disappointed if Grievous had just been set up that way in the micro-series as well.

Growing up I always rationalized the characterization difference as Grievous being pretty powerful right after his transformation, but slowly became weaker as his remaining organics struggled to exist within his cyborg body.