Las Vegas and Southern Nevada in general became a personal State for the Italian and Jewish mafias, an area they developed and owned by means of legitimate investments in Vegas that served as a cover for their criminal activities, turning Vegas into a bank they could use to fund their criminal operations but also to buy the politicians and public officials needed to keep law enforcement off their backs.
Then you add the crooked elements of organized labor in the 1940s, 60s, 70s, 80s, and perhaps even longer than that with Jimmy Hoffa, Sr., and company, which had all the resources they needed not only to stay in business but also to keep the politicians and public officials at bay and to send the message through their henchmen and hit men that messing with them would have a heavy price in terms of lives lost or ruined.
Las Vegas is the ultimate story of starting from scratch and building a major city with all the investments, businesses, and land as well as people to maintain these operations. The American mafia, Italian and Jewish for the most part, had a huge role in this along with the people they brought with them. As in government and organized labor, it took really clean, powerful people unconcerned about whether the mafia would destroy them to bring down these characters.