It was 2016-17, SE MT, 4 years post ~300,000 acres burning on the Custer Nat'l forest. Lower deer numbers post 2010-2011 winter and a huge turnover in habitat in 2012 with those fires caused an incredibly rapid increase in MD populations (I know no one here believes FWP data, but anyone familiar with those areas noticed how many deer suddenly appeared on the landscape).
Then you get drought, habitat senescence post fire and the effects of over-browsing during droughts and winter and there is less carrying capacity on the landscape. Those burns are not nearly as productive for mule deer as they were in 2013-2018 or 2019.
That population "explosion" was a blip in an otherwise downward population trend.
I'm saying compare aerial photos for conifers (junipers) from the 30's to present day. You could even pick the 50's. Conifer encroachment is, generally, bad for mule deer and good for elk, from a habitat perspective.