There are many reasons Mule deer struggle. It isn't just the fault of one person or an agency. If there is one thing that may be the root of it...well it may be $, and the human desire for progress.
While I've hunted SC Idaho for deer on occasion and Northern and Central Utah. It all looks about the same. I was raise in SE Idaho during the boom of Mule Deer and my ancestors all hunted them. I have returned there almost every year with a tag in my pocket since I started hunting in 72. Here is my observation of what has happened. Question is, can it ever be reversed? I doubt it. Stabelized maybe, but I doubt there is enough $ to put a few things back in place.
Hate em or love em the grazing industry, sheep, in the 30-70's put browse, particularly sage on the map. They manipulated the grasses and kept the browse coming. As the wool industry went south, so did our coyote control, and range manipulation. Grass now helped the elk populations grow and created another competitor for mule deer in the winter.
Add to this all the "everybody gets everywhere, because of motorized vehicals, and we are where we are with deer. The SE Idaho Mule Deer Initiative Program by the IF and G is at least taking steps to try and understand where we are at and if anything can be done. Itis an interesting program. You can check that out on their web sight.