Same reason the SCOTUS dealt a KO to the SCOFLA in 2000, I guess. States' rights go out the window when the state is oppressing its people on such a fundamental level, IMHO. But then, I'm not a lawyer.
Not a prinicipled (pun on screenname intended) believer in states' rights are you? You don't like the court's decision so you want the federal government to create a jurisdiction claim. How often do you want the federal government to step into state matters?
A believer in states' rights would say that the Nevada Supreme Court has the ultimate authority to interpret the laws of Nevada. The proper course for Nevadans to take after this miscarriage of justice is to kick their Supremes out of office through political means.
US Constitution, Article 4, Section 4: "The United States shall guarantee to every state in this union a republican form of government".
The Federal govt as a positive, explicit duty to guarantee that no state shall be taken over by a dictatorship, whether that dictatorship takes the form of a corrupt party machine deciding it can ignore elections, or a bunch of black-robed judges thinking they can ignore their state Constitution
The Feds have an explicit, Constitutional duty to step in in cases like this, where the explicit will of the people of the State is being defied by those who pretend to act under color of law