I’ve never done any sort of significant study of CRT or been very interested in it, but I had not heard this before.
My understanding is that critical race theory developed from Critical Legal Studies, which came about roughly a decade after passage of the Civil Rights Act to theorize about the stagnant condition of African American communities despite the emphasis on facially race neutral laws.
My understanding of critical theory, more broadly, is that it provides a critique of a society that draws from multiple social sciences to attempt to explain societal flaws and attempts to use historical context to explain how those flaws came to be in order that they be remedied more easily.
As I understand it then, critical race theory posits that the relationship between races in the United States is a complex social construct that is a product of multiple factors with a specific focus on US history and it continues to be perpetuated by the effects of those historical developments such as the accumulation of resources by white Americans, creating sort of a feedback loop that was not broken by the passage of the Civil Rights Act.