[BBell]

From the link at post 7.

In reality, everyone had ample time to escape. Mount Vesuvius had slowly been building up steam and giving signals of an imminent eruption. Unfortunately, it was also the festival of Volcanalia – the god of volcanoes. The Pompeians took the smoking and spurting mountain as a good omen, instead of a warning. They celebrated instead of evacuating.

[jmacusa]

Actually up until that time no one had ever seen a volcanic eruption. The Pompeians had no idea what was about to happen to them. Their tragedy was one of ignorance, not arrogant pride.