Partly because of brand loyalty.
Partly because there is no cheaper compelling electric Audi. If Audi had Model 3 clone at Model 3 prices I very much doubt Etron outsells Model S/X.
Partly because Model 3 is cannibalizing Model S sales.
And only partly because some prefer Audi interior.
Of course it’s always multiple factors! But whatever the reason, Model S sales have dropped a lot. Maybe this is the sustainable level, but I think they could sell more.