Reason
After Leonel was settled in, he became shocked by this sudden change. The Empire was attacking Camelot?
No, maybe he wasn't so surprised about this much. This was the way of The Empire, ever since they had taken power, they had never allowed any true threats to their sovereignty to survive. Maybe only the Slayer Legion could accomplish such a feat, but even then, they had only been able to do so by hiding away and tucking their tails for decades on end.
However, compared to the Slayer Legion, Camelot's location was laid bare for all to see. There was no chance to hide or be covert, and maybe even they weren't aware of why they had to do so either.
As far as citizens of Camelot were concerned, they were in the same location as they'd always been. As for their rulers, many of them might have an inkling, but only Mordred knew exactly what was happening thanks to the trial grounds she shared with Leonel.