From this website, which provides a lot of detail on the AD 79 eruption:
Until the 1980's it had generally been assumed that Monte Somma was prehistoric and that the 79 eruption, though tragic for the unfortunates buried in Pompeii, and for Pliny the Elder, who died while investigating the disaster, was otherwise fairly routine. That all changed in the 1980's when excavations in Herculaneum found hundreds of skeletons of people killed by the eruption, and improved understanding of pyroclastic flows led to better recognition of them.
It now appears that the eruption was a lot more disastrous than once believed and that both Pompeii and Herculaneum were buried by pyroclastic flows. The drop in pressure in the magma chamber allowed the summit to cave in to create Monte Somma, and the present cone of Vesuvius is the result of eruptions since 79. The few Roman depictions of Vesuvius on wall murals all show the volcano as a single cone with no hint of Monte Somma. In addition, medieval and Renaissance depictions of eruptions invariably show the summit of Vesuvius below the summit of Monte Somma instead of substantially above it as it is today.
Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.