The challenge of course is that in the absence of a silver bullet solution, that people working to combat all forms of child exploitation are simultaneously trying several things, ranging from going to the source as you suggest and arresting people, to trying to interrupt the online tools that they may use or that might fund/support them, etc.  So they don’t approach it as a binary choice between trying these ecosystem measures vs going to the source – they are working all the levers.

It is unfortunately a very difficult problem. FWIW, a recent NYT article on this was interesting – see https://www.nytimes.com/interactive/2019/09/28/us/child-sex-abuse.html Headline is “The Internet Is Overrun With Images of Child Sexual Abuse. What Went Wrong? Online predators create and share the illegal material, which is increasingly cloaked by technology. Tech companies, the government and the authorities are no match.”