I just can't comprehend it. it just makes no sense.
Why? Its extremely simple. Lots of human institutions operate on very similar principles. Well, you have a lot of intersecting interests and beliefs that lead to roughly the same outcome. Which I guess thinking about it can make it look complex, when its really a bunch of simple, self reinforcing concerns that push in roughly the same direction.
1) Protection of brand: If only, say, Indian music made by Indians is authentically Indian, then that creates a walled garden of a market where only Indians can compete in the Indian music scene. You then have several different groups that push for brand protection too, complicating it:
a) Customers: Consumers of Indian music desire "authentic" Indian music. There is perceived, potentially real, value in the authentic good, vs imitations, even very good ones. So, even if you a white Californian consumer of Indian Music, you still might want to gatekeep the "scene" of authentic, real Indian music. So, your anti-cultural appropriation because you want to preserve the authentic foreignness of the thing you love. Or authentic localism of the thing if its your native culture: I could see some indians railing against non-indians bastardizing art they don't really understand, or cultural traitors Americanizing a previously authentic thing.
b) Creators: If your an Indian producer of Indian music, its in your interest to not have to compete with the whole world: competing with all Indians is hard enough! Especially if you want to get into something very lucrative like an American market, where an American learning the austhetic of Indian music and modifying it to American tastes in America has an advantage over someone bringing Indian music from India into America.
Now, part of the strong inauthentic aspect of cancel culture is that it often manifests on the left, when many of those impulses above would seem otherwise deeply conservative. Claiming for example the only real Champaign is Champaign from Champaign, France makes more sense as a conservative policiy than a "liberal" policy.
This I think comes down to the left is generally the faction of ethnic minorities, who are the ones in possession of culturally distinct stuff that's valuable to protect. For example, if the only "authentic" Jazz musicians are black musicians from New Orleans, well, you've created a very valuable carve out for Black Musicians from New Orleans, who are going to be very jealous of their carve out. Or if you make it so anyone who plays an Indian (feather) in a movie has to be an authentically blood indian, well, that's a valuable carve out for all the Indian actors.
So, politically its a way of creating a bunch of special interest carve outs who will support you utterly because they depend on you for the carve out that makes their livelyhood.
Though you also don't want to put it to total cinicym either: something is generally powerful when you can get both the bootleggers and Baptists on the same side: so the purely mercenary and true believers push in the same direction.
Just about everyone does feel ethnic risk at some level: Even somewhere like Japan that very aggressively embraced western values and general westernization, did not whish to stop being Japanese. Even they have some limits to how much they were willing to copy and paste the West into Japan.
A black family living in a white country has legitimate reason to fear they're children losing the black culture and adopting a white one. If they value that black culture, preserving it against the majority likely requires active effort to police that boundary. To the degree then being anti cultural appropriation is being pro the preservation of minority culture, well that's responding to a likely real concern.
This unfortnately has turned into a quite long and rambily writing over a "simple" thing, and not really complete. I'll post this now, and if this conversation doesn't die before I get back, maybe then see if I can edit it down into something less stream of concensusness.