I'm sorry for their misadventure but an answer to the question of what could have been done different is, or should have been, obvious. Especially for "longtime Anchorage trail users." Off the beaten path in a highly populated with chronically stressed moose area and your dog is loose. I think the math is simple. You are pushing it. For the record I have done a lot of "pushing it."
The last thing I want to see is efforts to control the moose/wildlife or efforts to restrict  the people. I do however put all the onus of good decisions directly on the people. 
If you don't like conditions of an area containing stressed wildlife - then stay out. Otherwise exercise due diligence and have a fun and relatively safe time.