Q: Why was this article moved from Kiev to Kyiv?
A: In short: both are common names in use, but according to consensus in the last discussion the title Kyiv satisfies more of Wikipedia's policies and guidelines, including WP:MODERNPLACENAME and WP:NAMECHANGES. This conclusion was supported by a rough consensus of two to one by participants in a very long debate on the article's discussion page, and the title was changed on 16 September 2020. You can read the full rationale and discussion in the talk archive: talk:Kyiv/Archive 7 § Requested move 28 August 2020.
Q: Can we move it back to Kiev?
A: A one-year moratorium on move requests for this article was in effect until 16 September 2021. Please take all discussion on naming the article to talk:Kyiv/naming and start a discussion there before opening a move request.