Not totally irrelevant. Just because they were all under one central authoritarian rule, didn't mean that the Russians didn't consider themselves to be Russian, and the Ukrainians Ukrainian, etc. From what I read the transfer did raise a few eyebrows at the time, even if that was all.
I've only just learned that Nikita Krushchev was half-Ukrainian. That might explain why he gifted the historically Russian Crimea to Ukraine in the first place, hence indirectly causing the current mess.