The phrase “in the flesh” refers to the life that these deceased saints lived on this earth. Those who judged them in this life were other people, authorities or folk of the community who scorned their choices and made them suffer in some way. This was all very consistent with the way people do things (“the way people are”).
6 For this is why the gospel was preached even to those who are dead, that though judged in the flesh the way people are, they might live in the spirit the way God does.