Agreed that it isn't limited to Russians, but I do think there is a scale difference when it comes to the ultra-wealthy from Russia.

For example, when I was home in London a few years ago we had dinner at a fancy Chinese restaurant in Mayfair. My wife and I were chatting with the Maître D' for a bit, and he told us that they scheduled their host staff such that at least one person was present at all times who could converse fluently in Russian, in order to cater to their big spenders.

I know this is only an anecdote but I do think it is uniquely specific to Russian oligarchs. Aside from Harrods, which have specific staff to converse with the wealthy from China, the ME, etc. I didn't encounter a similar form of catering/pandering to the wealthy Chinese, Middle Easterners, etc. elsewhere.