Here is the relevant portion of the NV code - lists multiple possible reasons, and of course it was the second one:
Grounds for Initiating Disciplinary Action or Denying Licensure
NRS 630.301 Criminal offenses; disciplinary action taken by other jurisdiction; surrender of previous license while under investigation; malpractice; engaging in sexual activity with patient; disruptive behavior; violating or exploiting trust of patient for financial or personal gain; failure to offer appropriate care with intent to positively influence financial well-being; engaging in disreputable conduct; engaging in sexual contact with surrogate of patient or relatives of patient.
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3. Any disciplinary action, including, without limitation, the revocation, suspension, modification or limitation of a license to practice any type of medicine, taken by another state, the Federal Government, a foreign country or any other jurisdiction or the surrender of the license or discontinuing the practice of medicine while under investigation by any licensing authority, a medical facility, a branch of the Armed Services of the United States, an insurance company, an agency of the Federal Government or an employer.