Sounds like somebody forgot the old adage about not putting all of one’s eggs in one basket. For something this critical, why not have at least four vault sites in various locations / geologies?
There are about 1700 seed vaults. Each one can make a contribution to the SVALBARD vault. It’s like a safe deposit box - for each of the various others to store their seeds in case of regional problems.
One such vault was located in Aleppo-Syria. I have my own seed vault. I plant heirloom seeds, and save them. Plant my own taters, and plant the leftovers etc.
The location was chosen because it was far enough above sea level that even if both ice caps melted, it would still be above sea level, but it is an abandoned mine IIRC.
However, it appears that they forgot about rain and flooding, so they are going to have to modify the entrance. The water didn’t get far enough to go into the vault itself.
The seeds are stored in 3 ply mylar type bags and sealed, so theoretically, would be safe even if the environment was a bit damp.