Heavily outnumbered ≠ Ineffective in combat Honestly, the Clones were an attack they weren't ever going to be prepared for. They built bonds with them, and in doing so trusted them with their lives. So when the hammer fell, was there any way you could see them coming out of that? Surrounded on all sides by trusted allies now turned enemies? And same goes with the droids. Spartans were killed by common infantry all the time. It's a natural thing.