For Christians, it is an expression of reverence for Jesus Christ as the King of Kings, as stated in verses such as Matthew 21:5 or Revelation 17:14.
“They will wage war against the Lamb, but the Lamb will triumph over them because he is Lord of lords and King of kings — and with him will be his called, chosen and faithful followers.” Revelation 17:14 reads.
But of course, not everyone sees the expression for what it is.
One such person is Daily Wire host Andrew Klavan who claimed that the groups who say “Christ is King” belong to an “anti-Semitic crowd.”