It could be that Trump is just making sure his other avenues don't collapse at the last minute. It may also be he needs NV and could lose the election without the state. I honestly don't have a good sense either way.
NV may be crucial
NV was important to his paths. Without it, the paths narrow considerably. He then needs either CO or NH...or just PA. And that assumes he gets FL. If he loses FL, he needs PA and MI, then one of either NH or CO.
It is a nice cushion