It was indeed fortunate that they knew enough to quit.
They didn't know enough to quit, that's the point. I had the date wrong, this started more than 200 years ago, but continued for about 150 years.
[snip] It is uncertain how many papyri were originally found as many of the scrolls were destroyed by workmen or when scholars extracted them from the volcanic tuff. The official list amounts to 1,814 rolls and fragments, of which 1,756 had been discovered by 1855. The inventory now comprises 1826 papyri. More than 340 are almost complete, about 970 are partly decayed and partly decipherable, and more than 500 are merely charred fragments... By the middle of the 20th century, only 585 rolls or fragments had been completely unrolled, and 209 unrolled in part. Of the unrolled papyri, about 200 had been deciphered and published, and about 150 only deciphered. [/snip]
https://en.wikipedia.org/wiki/Herculaneum_papyriBasically, had they just left them alone...
Compare this with the Oxyrhynchus papyri fragments, which have a similar blackened appearance, but were not carbonized. They couldn't be reliably read and transcribed until recently, when different spectra and enabling technology was used. The dry conditions of the ancient Egyptian trash dump had preserved 400,000 fragments. Unknown fragments of plays by Sophocles and Euripides, New Testament fragments, and poetry from as far back as the 7th c BC has been identified. Should be an interesting few decades of work to come.