I haven’t played Ragnarok yet (for context on possible explanations blowing this idea out of the water). Though both Greek and Norse gods are “immortal” (both mythologies attribute this quality to them and some sources cite this as being given by eating ambrosia and idunn apples respectively) death and weakness among the gods are more commonplace in tellings of Norse myths. This with other factors gives the impression among most that the Nordic pantheon is weaker or at least more mortal than the Greek. I’ve taken away that it’s possible Kratos merely existing in this land where gods are perceived this way (by the audience at least) could be a factor in how he appears as weaker too. As an outsider god he may possess more power than them, but he’s now fighting kind of their rules regarding how gods operate.

(And obviously there’s other reasons that make more sense, the largest being that there just wouldn’t be a game if he was curbstomping these fools like he probably should be)