Everyone? It was the count's own mansion and the count was controlling the monster. So his people would be watching not the monster but the princess, the elf and the beastkin girlThe beastkin child was seen eating cakes and then disappears when the commotion starts, everyone's eyes are focused on the Elf struggling with the monster at range with her bow and magic, and the princess that's being shielded by knights and maids. then there's a bright light, the armor is empty, and the beastkin appears to comfort the princess.
They would know princess did nothing, elf was there and the beastkin disappearing would be most suspicious. They may even seen her appear with the elf