As to this part - it most definitely does not only infect superpowered beings - we’ve seen Iron Man, Hawkeye, Kingpin, Doc Ock and a bunch of other characters who have no powers, or gain powers only from gagetry.
The key is they’re all Heroes and Villains. They’re the strongest. Which leads to 2 possibilities:
They’re the strongest, so they survived the zombie attacks to become infected, rather than lunch. This is simple, but, I prefer option 2.
The virus has a magical, or quasi-magical nature, and partially sentient, to the extent of being able to invoke shifting priorities. Specifically, start by infecting the strongest - the Heroes and the Villains - then consume everyone else. As the virus infected several characters who shouldn’t be infectable by a natural disease - Ghost Rider, Wonder Man, Vision - and the behaviour of the zombies seems to follow this pattern, I think this is the stronger of the two theories.
I was very excited when I first read an article saying that Ben Grimm was Jewish. As a kid, I had searched for Jewish superheroes. Outside of characters-from-all-nations groups like The Global Guardians, and Sabra, I only found one. When the X Men fight Dracula, Kitty Pride tries to ward him off with a cross and fails, because she does not believe. Then, Dracula burns himself when he accidentally grabs Kitty’s star of David.
The Thing was being a Jew was a huge deal for me. Then, Fenris corrected me. Kirby may have meant for the Thing to be a Jew. There are some recent comics which adress Ben’s Judaism. BUT, there are plenty of issues over the years that show a Catholic thing, and What Ifs that show Ben as the groom at Christian weddings.
Ben was created as a Jewish character. Then, he spent decades as a Catholic. Then, a few issues pretended that he was always Jewish. At best, we have a retcon saying ‘He was always Jewish’. At worst, we have a lie that ‘He was always Jewish and it just never came up before’ which ignores all those times in church.