First: I am not a pilot. Only held a PPL-A long ago. I have a foot in the geosciences. Found that forum and thread by accident (nobody was hurt :-)) when reading this a recent Nature paper about "Future Changes of Precipitation Patterns Over the Arabian Peninsula" and searching for info on the flooding. I have been to the area (Sharjah, Dubai, Oman) on 2 occasions beacuse of archeology.
waito is right, cloud seeding was not involved here, besides its effectiveness being discussed controversally (depends on study ...), does not create rain just like that. Its intention is to cause clouds that have already formed and are in pre-stages of storms or potentially heavy rain (like the castellanus or congestus families) to condense and release their water prematurely, changing amount and place of rainfall.
The UAE do try to use its effects in a "weather enhancement program" (changing the place of the rainfall) to receive more rain that would otherwise just pass over as highly humid air or clouds. But as the UAE meterological office NCM said and reported by several news sites to debunk an earlier Bloomberg report, there were no cloud seeding operations at that time. That was a completely natural phenomenon.
It was said upthread that in Europe an equal amount of rain would have caused more damage. Well saidly that's true, but it has nothing to do with local (dis-)ingenuity!
Reports have it that in some places 250mm/m^2 of rain fell in less than 24. That's about the same amount (240mm) in 22h that caused a devastating flood in the Ahr valley in Germany in 2018. But ...
First: those drainage systems in mid range mountains have a huge catchment area and channel the water that runs off on the surface (is not stored in soil, for instance because that's already soaked) in river courses of various types.
Second: water running of in riverbeds of various narrowness, depth and slope has much more energy than the standing water we see in the images from Dubai. This creates erosion and even landslides, a mixture of water, mud, rocks, foliage up to trees, and further on parts of the infratsructure, technology, stone constructions ground to pieces and sadly animals and humans as "clasts".
So these are events in regimes of different energies involved, the outcome can't really be compared even without the usually unavoidable blaming of ... well whoever is to blame :-)
Stay safe evrybody
p.s.: Am not allowed to post links so tried to give info for own search.