Not that people haven't tried.
Lucas consistently portrayed the Mandos as scum; the TCW warrior Mandos (early in the show's history when Lucas still had some influence) are Space Jihadists who kill innocent people and terrorize civilians, a far cry from the heroes that Filoni will turn them into later. Whereas the movie-verse Fett Mandos are guns for hire who work with Sith Lords and criminal scum; they have no problems trying to kill innocent people, (LOL Padme) and always die like chumps. (Boba vs. blind Han, Jango vs. Windu)
Revan took down the Mandos at their best, when they had an empire of their own, turning them into a civilization of bandits and has-beens, and Kreia spends a short while shitting on them.
SWTOR had them lose to pirates and grunts in the lore videos, while the game proper just has them be mauve-shirts for the Republic characters to smack around.
Legacy had them get annihilated in the Battle of Botajef by a bunch of Stormtroopers, dudes that the Empire scraped off the streets and handed plastic armor and guns to. This is the last proper battle the Mandalorians have in SW Legends, which means their military history as a whole ends in shame.
But I suppose making the titular Mando go full "MUH KWEEN" did the trick, eh? Nothing like reminding them of another bad series to make them lose their taste for the Mandalorians. That probably did more damage than Jack Black and Lizzo. People were interested in seeing their hero, Mando, become king of his own people, and he chickens out and passes it over to a former terrorist who already failed at ruling multiple times.