This is a channel I watch and around the 3 minute mark, he mentions that there is only one source from around the time of eruption of Mount Vesuvius that makes any mention of it. I trust this guy as he seem to at least try to do good research, but it seems amazing to me that we only had one real record of it, given a mountain exploding seems like something someone would mention. Even if just in tax records or similar that thousands of people were no longer paying taxes. I tried googling around, but nothing seemed trustworthy. So I wanted to see this claim accurate.
I perhaps wonder if he meant to phrase it as - one eye witness account of the destruction of Pompeii. For that, we have Pliny the Younger whose uncle perished during the eruption. These were letters he wrote about the experience and were recovered in the 16th century. It's the only eye witness account I am aware of, but keep in mind it's the only one we have found.