- The convention rules were unfavorable for Sanders
- A large number of Sanders delegates (in the range of 50-70, enough to sway the majority) were disqualified and unable to appeal for various reasons, including not registering with the Democratic Party by the May 1 deadline and missing personal information
Sanders supporters called for recounts and appeals, both of which were declined due to the event being past its scheduled end time for the day. Due to Sanders supporters remaining in the venue after the end of the convention, law enforcement was called in to evict them.
Convention and election rules being unfavorable to Sanders is nothing new, so the news of the convention in Nevada is not particularly surprising. Exactly how much corruption is at work here is pretty questionable in my eyes, and Clinton's lead is still large enough that the few delegates that could have gone the other way here would not have made much of a difference. Sanders just isn't pulling the large majorities he needs to win the nomination at this point.