Wasn't there a failure in Scandinavia recently?
Floods happens all the time in the west, people dying from floods however is rare since when they happen we know why and how and when it will happen so we can evacuate people.
Libya failed to warn the people here, that is why so many died, that is the most significant failure and should have been the easiest part, it shows severe problems with their management of the dam. They should have known how much stress the dam can handle, and that this storm was likely to make it fail, and evacuate the people when failure was close.
In the west we would just say "the dam will likely fail due to bad maintenance", the destruction will be costly but lives wont be lost, and in many cases we can prematurely destroy parts of the dam to avoid destroying downstream infrastructure and that way come out of it almost scot free.
In my part of Germany we had a severe rain storm this week that caused local flooding in part because the sewage treatment plant could not process the intake quickly enough, resulting in the sewers getting backlogged while rain was still pouring down.
Even without outright neglect a lot of infrastructure simply can't handle situations significantly outside the standard range of operation.
It isn't luck, if Germany had earthquakes they would have built the bridges differently. You don't build things to handle situations that doesn't happen.
Our forests died because the trees we planted can't cope with the kind of heat waves we're now seeing. Our towns get flooded because our infrastructure wasn't build to handle this much downpour. But luckily earthquakes aren't something we have to worry about as much, climate change or not.
I bet somebody knows this. And that is the question that imposes culpability, not the ones you asked.
But if you are not going for culpability and just assumes everybody is honestly trying to improve, the question to ask is "was it properly maintained?"
Would this dam have failed eventually? Probably yes, on a long enough time-scale. Would it have failed now if not for that storm? Probably no.
Note that even in the developed West there are plenty of pieces of infrastructure at risk because of climate driven extremities.