Audi RS6 Speed GT cars were cheater cars, period, they paid to get series rules modified for their end result, were full tube frame in a street base class, had a significant aero advantage, and had the floor pans modified.
The Audi Quattro Trans Am cars were significantly superior to anything else running in that series, not to mention like the RS6’s that followed 20 years later, they were full tube frame opposed to cars with mostly production shells they were running against.
Yes the 10/90 AWD split in those cars helped them significantly with tire wear and rain traction, I will not deny that. But to say there were not other factors involved is ignorant.