//It’s not “sudden” NJ
It’s just you’re only noticing it now.//
Well apparently a campaign to secure the rebranding was only launched in 2018:
https://en.wikipedia.org/wiki/KyivNotKiev
I'd call that fairly sudden.
Apparently the Ukrainians had been trying since 1995 to get English language media to use the name but without much success:
"Prior to 2019, there were few cases of organizations switching to the "Kyiv" spelling, because many people outside Ukraine did not see the need or thought that the issue was "imposed by nationalists on purpose".
Personally I had never seen the alternative name used until this latest bust-up and quite honestly I had no idea where they were talking about. I guessed it may have been Kiev they were referring to because of the similarity. I actually see no point whatsoever in trying to persuade people to use their preferred name; it's only because the place has suddenly become fashionable that they've had the opportunity to reinforce their wishes. The next thing will be the UK trying to persuade the French, Spanish and Portuguese to call Londres London.