Why? That relies on a previous conception of Anu and Padomay as static forces. Why must they be so?
The Anuad doesn't cover the existence of the et'Ada before the creation of Mundus. These spirits were aware of the world before creation and presumably passed this information on to their children - mortals. If Padomay could act, then why would there be all the myths about Lorkhan (the Soul of Padomay) doing what Padomay did? The spirits surely would have observed the difference between Lorkhan and Padomay.
Again, why? Why is it infeasible to suggest that some myths simply got a few things wrong and were never corrected?
Both the death of gods and their departure are significant events. You could assume that they only observed parts of the whole history, but they're not the sort of events that get added by mistake. Especially not because people were around to watch it and aren't relating fanciful stories but history.
Must the gods always be looking over mortals' shoulders to grade their work?
That would certainly solve all those discussions people are having about religion, and yet not asking god for a confirmation is seen as a sign of faith. If there was ever a good way to know that you're being conned, there it is.
The et'Ada don't rely on faith, allot of cultures actually paint them as their ancestors. There actually is nothing against humbly apologizing to mother Morwha for not listening closely at the campfire ask if she could set you straight.
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Dug up two threads slightly related. Among other things it touches on the aspect of the gods being mutable now while they shouldn't be as they once were et'Ada allong with the Daedra.
http://www.gamesas.com/bgsforums/index.php?showtopic=422404
http://www.gamesas.com/bgsforums/index.php?showtopic=485557