I think this gets it right. If criminals know somebody holds a significant amount of crypto, such as the CEO of a crypto company, they don't need to have them

I think this gets it right. If criminals know somebody holds a significant amount of crypto, such as the CEO of a crypto company, they don't need to have them contact somebody else to withdraw and deliver a large amount of physical cash. They don't need to convince anyone they're serious. If the victim has their phone with them or can remember a password, then the criminals just have to coerce the victim into making a transfer. Arguably, this isn't even really kidnapping in the traditional sense. It's high-tech mugging. Owning a significant amount of crypto-currency and carrying the ability to make a transfer around in your head or pocket is basically the same as carrying a suitcase full of cash.