IMHO the reason people are fascinated by zombies is for two reasons:
1) One can imagine defending oneself against slow moving hoards of attackers - you don’t have to have superhero strength to do that. You can be an everyday Joe.
2) You actually get to imagine having an excuse to kill another “person’ guilt-free.
3) U.S.society (the most recent generation) is now blessed with a population that consists in large part of perpetual adolescents physically and emotionally.