It is not hard for people living in modern Paldea to grasp what it was like to be at the bottom of the empire's social structure – or, for that matter, to approach, but fail to reach, its apex. The material deprivation of antiquity's urban poor has no modern parallel, and those defeated in the Pokemon League, unlike those who failed to become Emperor, can content themselves with the knowledge that they were defeated in fair competition – not by an opaque, behind-the-scenes political process, the causes of its frequent coups often obscure even to the winners – and that a deep tournament run is itself a source of significant prestige.
Many who lived in ancient Mesagoza undoubtedly wished to burn it all down. The idea that a fish, of all creatures, was responsible, likely originated as a joke; everyone was so bitter and jealous during the years leading up to the collapse, and anything seemed possible, even an aquatic creature setting Paldea's Great Fire. Chi-Yu believers, however, can point to a far better attested counterpart; if Slugma and Magcargo can adapt normally aquatic body plans to lava, why not a fish pokemon?
A relic does exist of Chi-Yu in Firescourage Shrine, in the form of a set of beads, which are popularly held to be the pokemon's eyes. The beads are genuinely ancient and remain hot to the touch, but they do not in themselves prove the existence of a fish made of fire – let alone that said fish perpetrated the Burning of Mesagoza. Yet Chi-Yu believers universally wish to keep such a tragedy from repeating, not to make it happen again – so why, then, did multiple wealthy and prominent skeptics of this pokemon's existence pass away in house fires?