He would have beat the best striker he has ever faced, quite possibly cementing himself as the best fighter ever to compete, or at least within reach in a few fights. Regardless of that, what do champions gain from defending their belts, but money and added legacy? Of course they have the most to lose, simply by being champion. However, that wasn't the main point, you've created your own narrative on how bad all Conor fans are and how they are discrediting Aldo, yet I haven't seen one post here about that.
I haven't seen anyone ever say that if Aldo loses to Conor then everything Aldo has ever done is for nothing, which is a ludicrous statement to make. In fact, even if Aldo loses to Conor, I rate Aldo's achievements at featherweight above what Mcgregor will have achieved up to that point. Just like Anderson Silva's is above Weidman's, despite Weidman likely being the better fighter.