The scrolls were smuggled out of Jerusalem and stashed during one of the Roman Wars / Jewish Wars. The only trace of the Essenes is in a single account of some hermits who lived in small caves along the Dead Sea (described in Josephus I think). The multi-storey building at Qumran was used as a working manorial farm, hotel, and maybe a whorehouse at different times during its ancient existence.
copper scroll treasure map
Google
So, remnants of the Temple Library, taken out of Jerusalem just ahead of the Roman siege and destruction of the Temple, and hidden there?