However, a number of factors eventually led to the collapse of the civilisations in the fertile crescent. One factor has been the region getting warmer and drier, which poses a challenge even with irrigation. As an example of how different the climate is now from what it was then, Uruk used to be on a channel of the Euphrates, but now that riverbed is completely dried up. Meanwhile, Ur was once a coastal city, but is now ten miles inland.
Another factor for the collapse of these civilisations is that the process of irrigation accumulated salt in the soil. The very process that made complex civilisation possible in this part of the world eventually contributed to its end.
I recommend the Fall of Civilizations podcast for more on this and other societies: https://www.youtube.com/watch?v=d2lJUOv0hLA
But they could still only have camels as their pack animals, since that's all they'd domesticated. It's not like camels will die in non-arid locations
Likely the animal was venerated as a meat source.
As recently as 5,000 years ago, it was a much wetter place.
If these people went as far as to carve camels in stones, that would mean these animals were prevalent in their areas and way of life which is in direct conflict with assuming their land were anything but hot and arid.
I have heard of the theory about different climate of Egypt and Iraq in ancient times. It seems logical that civilization should have started in a climate supportive for mass agriculture.
It's depressing when we think of earth's climate change over a time scale unimaginable for humans. The theory implies (at least for me) that the decline of quality of life in ME/NorthAfrica has more to do with a random external change not in control of insignificant humans.