A bit off topic, but with regards to CSAM: I don't understand the motives of people who share it online for free¹. Distributing child pornography risks serious consequences, and I don't see what the compensation is that makes people willing to take that risk for no monetary profit. Maybe if we understood that motivation, we could make it less attractive to do; preventing the motivation for the activity might be easier than preventing the activity.
¹ Which is among, of course, the many other things I don't understand about them.
Offhand I'd say there's at least 3 reasons. Notoriety - either pseudonymous or otherwise, bait - like a state actor, and as an attack or exploit against a site operator. This is assuming some definition of public where a casual user not searching for or desiring it can discover it.
So basically the same reasons as any other undesirable or "illegal" content being found publicly.
> I don't understand the motives of people who share it online for free
From what I have read, it's to share and / or (worse) collaborate. A distant example that I recall was a couple in US that sold their 12 year old child in marriage to an adult (the legal marriageable age, with parental consent, in MA and NH is 12 years old).
¹ Which is among, of course, the many other things I don't understand about them.