When I signed into this game world, after accidentally selecting Moorabbin! (i did my PPL training there, YMMB was just automatically typed in !), I selected Essendon, and then took a look around at the demand, while I was surprised at initial demand between Melbourne and Sydney at 150pax per day, when compared to Brisbane and Sydney having 1,000+ per day, I chose to keep my base at Essendon and play the game from there.
I'm glad for the challenges being presented to us in this game, and doff my hat to you on your market share on the Adelaide to Essendon route! (however, just checking now, I see you have closed one of your routes). I've taken advice from some of the team members in the alliance my airline is a 'proud' member of, and have a strategy in place to make the most of the demands that I am presented with.
If we were running a real airline today, would we have the luxury of hindsight to know that some major event for the decline in numbers, or a cause to drive them is just around the corner? This isn't real life, let's play the game with the scenarios that are presented to us, and make the most of the situation. Who know's what will happen to the demand in 1 - 2 years time ; )