Ok I know this is one of those things that makes too much sense. Therefore it would have lowered the entertainment value. But all they had to do once they got the safe open was lock themselves inside and ride out the nuke that was only minutes away. Then they just open the door and stroll out with all the money and no zombies to deal with. Jeez
shareThat is under the presumption that there wouldn't be a hotel sized amount of rubble in front of the safe door basically entombing them inside.
shareEven though it was mentioned it would be a "low-yield nuclear warhead", that would only mean a smaller impact radius. There would still be horrible radiation in all of Las Vegas, and I don't think anyone would actually volunteer to find out the effects of that if they had the choice to try to get out of there first.
And there is no way to know if that vault could withstand a nuke falling on it. It seemed to survive the blast, but that's only because of what Snyder chose to show. In real life, anyone willing to bet their house that the random vault they just found could withstand a nuke falling on top of it?