Our records of the state of pompei are stored in computers and books, which will decay a lot faster than buried stone. In 300 years, people might get bored of Pompeii and the records could be left in disrepair, or maybe contemporary retellings of the history will have picked up a lot of falsehoods due to natural drift. And this is to say nothing of the possibility of society collapsing due to climate change.
If Pompeii is buried, then in 1000 years archeologists can go check for themselves if the information they have is accurate. Just like we did.