One problem I have with the 'vidhi ka vidhan' is that it makes sense to say that after a task is completed - be it successfully or unsuccessfully. To invoke 'vidhi ka vidhan' either before, or use it as an excuse to gloss over evil, defeats the purpose of either people undertaking anything in the first place, or provides a copout against punishment of evil.
Obviously, gods can't micromanage things, which is why they put things in 'autopilot', if you will, and only intervene when things become out of hand. Like Ravan. When he was busy supressing good in the world, nobody excused him on grounds of 'vidhi ka vidhan'. When Sita was abducted, Rama didn't just let it go on grounds of 'vidhi ka vidhan'. So why is it 'vidhi ka vidhan' when Manthara plots against him, or the Avadhis start slandering Sita?🤔 Answer: it isn't, if one goes by Valmiki; it is, if one goes by Ananda Ramayan or any of the other wack jobs out there.
Since this story isn't there in Valmiki, trying a rational explanation of this wacko creation by the Sagars isn't really necessary. In fact, I don't recall Rama saying 'Vidhi ka Vidhan' anywhere in Valmiki - does he?
When Lakshman returns to Rama (7-52), he tells him, "According to your orders, I have left Jaanakee on the bank of Gangaa, near Vaalmeeki Muni's beautiful Aashram, and I am coming back just now. Hey Raam, Don't be so sad. Kaal's Gati is like that. People like you should not worry too much. Treasures get empty, progress changes into fall, people meet to separate and the end of life is death. Therefore one should not have too much attachment to sons, friends wealth etc, because they are made for separation. You are able to teach to all Lok, then why you yourself are so unstable? Ideal people like you do not feel attachment on such occasions. When you can console other people then it is not a big thing for you to control yourself. therefore you be patient and feel strong."
That's very different from the 'vidhi ka vidhan' line that is religion to the Sagars. If we simply follow Valmiki, none of this junk from other sources need confuse us.