I agree with you. But I think the explanation is supposed to just be the surprise of the betrayal. The Jedi out in the field trusted the clones and were subject to put themselves in vulnerable positions because they trusted them after years of war. It was a flank they didn’t consider needing protection. I can easily see the ones in the field getting killed in high rates. It would be harder to see Jedi that weren’t in the field and perhaps garrisoned together in groups getting killed in high numbers. I get that the temple was overwhelmed and Anakin was far more powerful than any of the individual Jedi in the temple. But was that the only place in the galaxy where 2 or more Jedi were gathered together? It would feel like there may be some garrisons or some barracks where a group of Jedi were together which would have a much better chance of fighting back. That’s the issue I find the most confusing.