For a Russian Oligarch London offered a community where other Oligarchs, western elites could mingle. The galleries, museums of London's are impressive but Dubai has some of the finest galleries/museums/restaurants in the world. They offer a wealth of everything and much more like Swim Amongst Sharks at the Dubai Aquarium and other things banned in the western world.

These things are tourist attractions. People who reside in a place don't usually habitually visit tourist attractions.

Dubai is vulgar place. Even an oik with a helipad on his yacht knows that.

Plus any multi billionaire can have world class chefs on retainer.

Part of the eating at exclusive restaurants thing is to see and be seen in public doing the things people know to be exclusive. Private chefs don't quite do that.