I'd suggest it started much earlier, and I would point my finger at Holocaust revisionists, lumped together with Holocaust deniers and antisemites in general, and generally canceled.
Sometimes put into prisons, sometimes chased with lawsuits and fined, more often simply pushed out of academia. It is so nice to have a certain historical narrative utterly unopposed, so it looks more like religious dogma than an area for scientific research and reasoning.
One may entertain varied, nuanced, and debatable views about the Armenian genocide, or about the Russian revolution. Perhaps the Armenians were not 100% victims, but also did something that provoked Turks? Certainly, many Turks seem to think so. Maybe, the Russian revolution was also morally complex, and there was no pure righteousness nor evil, no domineering moral heights to occupy? Pretty much everyone is allowed to think so.
Such views about Jewish recent history (or rather European history involving Jews) are not exactly forbidden, but they are certainly scary to entertain, even living in the most free-speaking country. It is a minefield only a maverick like David Cole dares to walk.
Thus cancel culture has proven to be an effective weapon to wield in the perceived interest of a certain ethnic, religious, and political group.
Perceived interest is simple: to occupy the highest moral ground and hold on to it, not allowing any pesky critique nor doubt to dislodge the occupiers of such a fortress.
Having high moral ground allows a relatively small group
occupying such a strategic position to effectively defend their territory and to launch surprise attacks, mobilizing the public opinion against advancing contestants, thanks to contestants being instantly recognized as morally inferior, not simply factually incorrect.
Most certainly this early cancel culture was also associated with political Left.
The USSR school system was built on a high moral ground of "Teaching of Marx-Engels-Lenin is immortal, because it is true". This circularly rounded logic allowed a singular viewpoint to persist while cancelling every opposing view until its permutations drove the whole immortal socialist State into a tailspin.
After that cancel culture was adopted by Feminists, and run for quite a few years, resulting in creating a regime of terror in academia, when male professors do not dare not only to speak against feminists, but also do not dare to show any signs of masculinity in the slightest. They learn to hush their voice and hide their hands, to appear as non-threatening as they could. Also, they learned that hiring preferences, awards, and promotions must go to the females first, which looks ironically like a return to pre-revolutionary France rules of politesse, where women are coming first in every instance.
Moreover, the usual historical studies, literary and linguistics courses had to shrink and shrivel to make space for the standard postmodernist - feminist discourse of oppression, sexual harassment, and so forth. One may not speak of women in negative terms, this is a sin of misogyny, which nowadays is much less forgivable than a sin of antisemitism.
Well, now this cancel culture, being so successful, is adopted and spread even further, and what is more ironic, it seems to have made a full circle. Black cancel culture won't give a damn about the Holocaust nor pay any attention to screeching feminists. New cancel culture wants to take the whole mountain of high moral ground and sermonize from up there down to us all. So far this general strategy has proven to be most profitable.