Taking possession of the ransom without getting arrested/physically followed by the police is what foils most kidnapping plots [1], and cryptocurrencies definitely address that part.

Criminals don't really need strong anonymity as long as the payment system has strong censorship resistance and at least one counterparty won't mind accepting "tainted" funds.

Arguably, privacy is much more important to non-criminal individual users as they themselves can be targeted by criminals as a result of their income/holdings being globally visible, and unlike organized crime, they often have less means to protect themselves from $5 wrench attacks.

[1] Source: I watched many crime thrillers growing up