The victims are not going to base a winning claim over the bringing in of guns in his luggage. It’s going to be based on the time between when the gunman shot at the security guard and now we learn the maintenance worker (who called hotel security, there’s an audio recording on the news) and when Mandalay called the police. If they dithered or delayed at all, that could convince a jury in my opinion.
As for claims against Jason Aldean, the concert promoter, etc. those are not going anywhere.
The best claim is against Paddock’s estate, but that won’t be nearly enough to compensate so many victims.