It was probably to open up the possibility of defeating Trump on 2 fronts in 1 state: DeSantis defeats him in the Caucus while she defeats "None of the Above" in the Primary.
Of course, DeSantis has dropped out, and the way things are going, None of the Above may be victorious.
DeSantis's campaign had the same criticisms of the caucus as Haley does, so they likely knew they weren't winning it
https://thenevadaindependent.com/article/desantis-super-pac-calls-nevada-gop-primary-rigged-for-trump-other-candidates-shy-away-from-stateNever Back Down, the super PAC backing DeSantis, criticized that decision in announcing that it was suspending door knocking operations in Nevada.
“Unfortunately, state GOP leaders are so obsessed with appeasing Trump that they’ve rigged their primary to prioritize Trump above their own voters,” a Never Back Down official told The Nevada Independent. “They’re eliminating important grassroots processes which doesn’t benefit voters, only Donald Trump, so it doesn’t make logical sense to continue spending resources on grassroots efforts like door-knocking in the state.”