The ‘Curse’ from Azura was likely just Red Mountain’s influence acting through her like a conduit, rather than a simple daedric whim

First of all, the Chimer were likely the merish race closest to the Aldmer in appearance and biology

The velothi exodus happened before summerset focused heavily on eugenics, Veloth was an Aldmer as were his people (i know its game design but ESO uses the Chimer model for Veloth), the only thing really separating Altmer from Aldmer is the eugenics which the Chimer obviously didn’t practice. We also know that merish races are shaped by the towers they are in proximity too, I take it that the Chimer becoming Dunmer was simply them finally activating their tower(via the tribunal) and thus changing into new forms. I find it very difficult to believe that Azura alone had the power to curse an entire race, regardless of devotion -this is the first era and the dragonfires are lit, the only other times we here of gods changing mortals’ forms is during the dawn