Didn't realize Ground Zero had over 10K, but it's been around awhile and probably the Falloutesque theme attracted a lot of attention.
Upon checking, it looks like Necromancer has over 10K as well, but again it’s been around awhile. There's probably a few more older stories over 10K around.
Always knew about Deadman though. Not really surprising Berka’s story gets a lot more attention. Zombies are always popular and it was written well with game elements which some people prefer.