I think there's a lot at work psychologically in advertising, but "kids in those countries have started collecting and trading those images" kind of undercuts your point that shock content doesn't resonate with an audience, create demand or a potential desire to emulate what's depicted.

From another angle, OP's article mentioned something akin to sexual awakenings related to the content they trafficked in.

You can see how popular suicide drone footage out of Ukraine is, there is a large contingent of people eating that stuff up, cheering it on, despite watching a man desperately beg for his life as a drone circles him, toying with him, before going for his head and the feed blacking out being about as grim as it gets.

People are creating games now to replicate the experience. People want to drive drones into other people's heads, all along a spectrum from watching it on youtube, playing a video game, to joining the ukrainian effort and actually performing the act in real life.

My experience is you can find a customer for just about any content, including shock content. Some messages have broader appeal for sure, but even the worst thing you can imagine will have someone with whom it resonates.

It's clear that people are influenced by their environment, and things that were once considered grotesque and unacceptable can be watered down over time with exposure to where, for example, rapists and pedophiles can openly win presidential elections and be placed on the Supreme Court. To where large portions of nations rationalize and support genocide, or any horrible thing you can imagine, even when presented with images of the suffering inflicted.

Humans are malleable and you don't have to have a perfectly crafted advertising campaign to have some people decide they like what they're seeing and want to replicate it, no matter what it is.