That's where the whole mother/son thing comes from, I think. If she's really god she'd just smite any pretenders to her throne or whatever, but if she pretends he's her son she doesn't have to answer any awkward questions about why she lets him keep doing it. You have to understand that she doesn't actually want to prove herself, she just wants to assert herself and have everyone agree.

And of course C can't help but play along no matter how stupid it is.