what happened here
Under Maric, the Kingdom still kept it's orlesian fashion(If more subdued) from the occupation days. Post blight Alistair and/or anora spearheaded the way for a "traditional" restoration.
Ancienct Alamarri/Fereldens dressed like this.
Maric dressed in a more half and half way, still keeping the Orlesian styles, but adding in a bit of the old barbarian roots of Ferelden.
Cailin who wanted to reunite Orlais and Ferelden under more peaceful means, kept a more orlesian style than his father as seen by the entire nobility in Origins who dressed like actual noblemen, just withouth the insane ruffles and the like we see from Orlais.
Where Ferelden fashion fell off a fucking cliff is during the reign of Alistair and/anora, both of whom have TERRIBLE fashion sense, and overcompensates in regards to ditching Orlesian fashion that they dress so "oldschool" that they no longer even resembles Fereldens at all, but neither resembles Orlesian style either.
I blame it on Alistair's wife not being there to reign him in.
The Ferelden court would have looked much more sensible if the Queen hadn't gone on her(Pointless given what happened) trek west.