The receptive helper verb means to receive (an action). It tells you that the action of the verb to which it is attached is being received.
Sometimes, a verb and it’s attached helper verb can be condensed and treated as a single verb.
This is not possible for the receptive helper, as the action of the attached verb is always done by someone different than the helper verb (first verb is action being given, helper verb is action of receiving this action).
れる/られる is always the head verb, not the verb to which it is attached.
The に particle marks marks a target when projecting something, some action, towards something else. It marks that something else.
In cases where there isn’t projection, where instead the action is being received from some source, rather than marking some target, に actually marks the source.
さくらは誰かにカバンがぬすまれた → In relation to Sakura, (her) bag got stolen by someone.
だれか (someone) is marked with に, they are the source of the action (ぬすまれた/got stolen), and the one getting the action is the が marked bag. This is because れる/られる is the primary verb, it is applied to the subject of the sentence, the subject is getting the action, and に is simply telling us more, telling us the source of this action being gotten.
A push sentence has one primary verb (action). に marks the indirect object (receiver). The target of the action.
A pull sentence has two verbs (actions), the base action being received, and the action of receiving said action. に in this case is marking the doer of the action being received, the source of the action.
The structure of the sentence is receiving sentences. The particles reverse their polarity.
Instead of に marking the target, it marks the source.
“Nuisance Receptive/Passive”/迷惑受け身
さくらはだれかにかばんがぬすまれた ← In relation to Sakura, bag got stolen by someone (receptive sentence).
さくらがだれかにかばんをぬすまれた。 ← Sakura got her bag stolen (nuisance receptive).
The nuisance receptive describes an actor as the receiver or a negative action, something unfortunate they received.
In any receptive sentence, the が marked core subject is the one who is doing れる/られる. This is because it is the last verb in the sentence, making it the “head verb” or primary verb.
Receiving an action doesn’t have a direct object, so を in receptive sentences marks the direct object of the secondary action (the action being received).
The presence of を does not necessarily indicate a nuisance receptive sentence, as it could be present in a regular receptive sentence also.