Not sure what the hotel really did wrong.
if the hotel hired a security guy without a good background check or without strong life-saving credentials who became corrupt and allowed Paddock to bring up firearms and also perhaps was paid off (took cash to Mexico, perhaps) to allow a "movie shooting" to be made with officially fake guns, until after it was too late he realized that these were real guns when looked down and saw that his leg was bleeding...
Then, yes, the hotel is 100% liable.