In this type of sentence, "The man is paid.", "the man" the receiver of the action of being paid, yet is it in Nominative case. Anyone knows why it is not in accusative?
Because the verb is in the Passive voice, so "the man" may be the receiver, but he is the subject of the sentence (nominative) , not the object (accusative).
The man is the receiver of the action of paying -- but he is the "doer" of the state of being paid!
We say "He is paid" with nominative/subjective "he" as well in English, not "him is paid" with accusative/objective case.