Predators, disease, over hunting, poaching or any combination of these could cause the decline.......................
Logical inquiries would shorten the study and hence the funding. Let's start with brain worms caused, indirectly by man made global warming.
Moose tend to go through cycles in their population. The herd has a good breeding season and expands. Then things return to normal levels. Then the “baby boom” moose all get old at the same time. They develop arthritis and become easy prey for timberwolves, or die of natural causes.
Then another good breeding year comes along and the cycle repeats. Timberwolves are on an inverse cycle (in down years for old moose, they can’t find enough to eat).
Nature knows what it’s doing. Stay Calm and Watch the NatGeo Channel.