>why is their religion different?
It's not. I hope none of you are autistic enough to get hung up on different names and a permutation of certain symbols.
Hammer or axe, Donar, Thor or Perun, why make a big deal out of it? Paganism is supposed to be above that sort of thing.
By the way, the cult of Deus Pater/Jupiter/Thor grew out of an earlier "axe cult", so Rodnovery in a way lies closer to the source of Indo-European symbolism than Asatru. The Romans retained the axe symbol in the fasces. Don't quote me on this, but I wouldn't be surprised if the fasces and the attached consular role had a function in Jupiter's rites.