It's all about the campaigns. Obama targeted NV and CO hard in 2008/2012. Those two states were bound to track right when he wasn't on the ballot. AZ was targeted much harder by Hillary than it was by Obama so it was an outlier in its D trend.
Colorado actually trended D in 2016. What else do you call going from 5.3% statewide to 4.9% statewide while going from 3.9% to 2.1% nationally?
I'll accept your point, even though it's a pedantic one about how one defines a "trend". The point I was trying to make was that Clinton's relative (to Trump's) level of support in 2016 was smaller than Obama's (to Romney) in '12 despite the fact that the state is undergoing explosive growth that made it demographically friendly to Clinton. An Obama-type campaign (rare as it might be) could have done much much better than D + 4.9%.
