Very good bio, DC. Thanks for posting it. Two points:
1. In his bio of Siegel, "We Only Kill Each Other," Dean Southern Jennings points out that Siegel didn't pull a trigger in the Big Greenie murder. He was the spotter who found Greenie. The triggermen were Allie (Tick-Tock) Tanenbaum, a Murder Inc. hitman; Frankie (Mr. Gray) Carbo, a Brooklyn Mafioso who later ran the fight rackets for the Mob in NYC; and Whitey Krakauer, who was Bugsy's brother in law. Of course, Bugsy was complicit, and the murder charge initially lodged against him was justified. The charge was dropped after Brooklyn DA Bill O'Dwyer (later mayor of NYC, later hastily appointed ambassador to Mexico) refused to let Tanenbaum (who was in his custody) go--fearing, no doubt correctly, that Tanenbaum would never make it back to Brooklyn alive if he testified against Siegel.
Second, according to Lansky's biographer, Robert Lacey, there were seven hotel-casinos in Vegas when Bugsy took up residence there ca. 1941, after the Greenie affair. Bugsy initially tried to horn in on the El Rancho Grande, but was rebuffed by the owner (who lived to tell about it). He then muscled in on the El Cortez, invited Lansky and other NYC hoods to invest, and sold out nine months later, doubling his money.
His next move was on the hotel that Wilkerson had already named the Flamingo. It was partially completed but, as you noted, Wilkerson ran out of money to finish it due to gambling debts. The rest is as you posted.
Siegel is widely credited with having "built" Vegas. His indisputable contribution was to envision a hotel in the Miami Beach style--all the other seven were in the Western "corral" style. But, as both of us know, Moe Dalitz was really the guy who "built" modern Vegas.