If the rabbi works at the shul, his son learned under him, and the son is a capable man with a suitable personality to fit the congregation, then wouldn’t the son have an advantage over his father’s hashkafah over even an unrelated student?
In this case, the son was raised at home.
I say this because:
The son may know answers to sheilot, according to his father’s hashkafah, and how the father would posken for members of his congregation.
The son would have seen his father interacting at home. Maybe he would have overheard conversations between his mother and father. Maybe he would have had access to teshuvot.
Also, he has life experience. Someone can come up and ask him what to do if such and such happens in the kitchen. Well, according to his father, when such and such also happened at home. Or, his father had access to numerous shailot and the son was exposed to so much.
The congregation may not realize just how qualified the son is. It is possible that it would not be modest if the son told This congregant and That congregant what he knows. So instead he looks like he is being favored without reason. While, the guy in the interview room from the next town over is new and different, and can add something to the community. He looks like a good catch.
At the same time, maybe the rabbi’s son is what the community needs to stay consistent and keep the balance and peace?
Those are some thoughts.