Christ Is King / Candace Owens Feud With Ben Shapiro

Answer: You've stumbled upon a developing ethnoreligious schism within the conservative movement – a fight between Jews and Christians that's spiraled out of the commentariat talking about Israel vs Palestine.

For background:
This mostly starts with a feud within the Daily Wire, a conservative leaning news and media outfit. It was founded by a Jewish man Ben Shapiro (amongst others). (Shapiro is not currently in management there, but is still on their commentator roster and is still influential.) One of their popular commentators, Candace Owens (a black woman), has been critical of Israel and its actions. This has eventually lead to her firing from the Daily Wire. The firing came despite earlier claims by current management that she was free to speak her mind.

Conservative commentator and author Auron MacIntyre (from The Blaze network) has attempted to summarise the Daily Wire fighting in more detail here.

As for "Christ is King", it appears to have mostly started from that "AF Post" tweet you linked, which excerpts from a longer video with Andrew Klavan. (Klavlan is a Jewish convert to Christianity, though he has … nonstandard takes on Christianity in his commentary still.)

"Christ is King" is a basic profession of faith for many Christians, so opposition to the phrase is going to be taken to be opposition to the faith itself (or big parts of it).

Things spiraled a bit out from there. There are a lot of posts, possibly too many to list, but some of the more standout ones include

Joel Berry, managing editor of the Babylon Bee, a right-leaning Christian satire site, posted a tweet saying "But we said ‘Christ is King’ on the internet!" accompanied by an image of people burning in hell. (The Bee later reposted a many-years old article which people took as a subtweet aimed at whites and Christians generally. After a very hostile reception to this, Seth Dillion, another head at the Bee, posted "When you're personally offended by a joke about white supremacy you might want to rethink some things, including whether Christ really is your King.")

James Lindsay, mathematician, self-professed "militant atheist", and participant in the Grievance Studies hoaxing posted a thread claiming that "Christ is King" is a "trap" "likely led by a fed"

So to Christians on X/Twitter, you have a mix of Jews, Jewish converts (some who don't seem to have wholly left behind their jewishness at conversion), and militant atheists telling them to stay quiet about a profession of faith of their religion. The choice for Christians then becomes sharpened to

Stay quiet and go along with the demands of people who are in opposition to them and their religion. Many would be uncomfortable at best with this, especially as there is the bible story about Peter denying Jesus before the c--k crows.

Demonstrate their opposition to the demands by repeating "Christ is King"

Many online Christians have (loudly) chosen option #2.

From the tweets that you've linked, a bit more context for the first two

This is Nick Fuentes, leader from the "America First" group and general pain-in-the-neck to many even on the conservative side. His open disdain of Jews in general makes him quite unpopular amongst a lot of people, though he does have a small hardcore following.

Brandon Herrera is a very popular firearms Youtuber and current challenger to an incumbent Republican in one of the Texas primaries.