I think you are wrong about Audi not wanting to win in MotoGP. Their main aim it to sell bikes and winning races helps sell bikes and winning at the top tier of racing is better still. That being said, Ducati isn't the primary priority of Audi and it never will be.
In Russia we have saying, "if it isn't broke, don't fix it". We also say, "if it is broke, don't fix it".