CRT went mainstream because many people equivocate CRT with a belief in, e.g., structural racism. Thus, opposition to CRT is now equated by those on the left to a denial of structural racism. The existence of structural racism has been accepted (at least tacitly) by most of American society for generations, which makes CRT on its face seem unobjectionable to non-academics on the left.

While I vehemently disagree with actual CRT scholarship because of its race essentialism and rejection of objectivity, it's kind of pointless to take that stance in regular discourse. It's not possible to explain to people that the concept of structural racism predates CRT by at least a decade[1], longer if we don't require literal usage of the phrase "structural racism". MLK, Ralph Ellison, W.E.B. Du Bois, Frantz Fanon, and many other writers were exploring structural racism long before the CRT school assembled. More generally, bifurcation of social analysis into structural and cultural began in the 19th century. (EDIT: There's another vein to CRT related to postmodern structuralism--which is not the same "structuralism" as discussed in earlier race scholarship or generally understood in mainstream sociology. CRT mixes and attempts to synthesize those distinct ideas.)

Similarly, CRT on the right has been thoroughly equivocated with Marxism and other radical theories. But Tucker Carlson is talking out his butt because actual Marxists have been scornful of CRT since at least the 1990s. Alot of the lexicon of CRT comes from Marxist discourse, but so what? Libertarianism arose from the American Anarchist movement and would still use a similar lexicon but for self-conscious scrubbing of its language. (The one thing CRT clearly shares with Marxism is belief in a categorical, singular cause of oppression--white supremacy in the case of CRT, class conflict over control of the means of production in Marxism.)

"CRT", like many things, has become another empty label thrown around in the culture wars.

[1] See pp4-5 of this 1964 Students for a Democratic Society (SDS) Bulletin: https://25thandclement.com/~william/links/pdf/SDS_Bulletin-1... It was the earliest use of the literal phrase I could find on JSTOR.

Marxism isn't crt

I didn't mention Marxism.

Not sure why you felt the need to

Honestly this shows the problem with many in america today.

Someone says they disagree with X. Instead of finding out what they think about X, instead people will decide that conservatives hate X, and then use the worst arguments made by conservative commentators as a strawman.

Moreover, even though there is wide agreement X is bad, since some conservatives dont have the right reasons, more energy is expended mocking conservatives than combatting the actual policy.