"some reason"It seems that Trump just does uncharacteristically badly in caucuses.
edit: Excluding Nevada, for some reason.
There is no "Nevada" there is only Las Vegas. Nevada has about 2.8 million residents and 1.8 of those are in Clark County... in other words, the Greater Las Vegas Metro Area. And that lovely above-depicted collection of golden glass and steel is right smack in the middle of it. Las Vegas is Trump Country, and Nevada is essentially the Las Vegas area surrounded by 300 miles of desert in every direction. Trump's win in Nevada is no inexplicable anomaly.