I mean cryptocurrency is indeed what made ransomware possible.
I have never heard of ransomware that predated cryptocurrency; could you share a link to an article?
It’s also interesting that all of those early anonymous remote payment methods have been significantly altered specifically to nerf their utility for extortion and scamming.
By removing that need, cryptocurrency makes ransomware scalable. And as Paul Graham and other Silicon Valley types have said a thousand times, scalability is the difference between a modest mom-and-pop operation and a rapidly growing enterprise.
In my mind, the catalyzing effect of a cryptocurrency in this context is from:
1. The ability to move something of value digitally
2. The thing of value being resistant to governmental control--crypto can't be easily seized, but a US bank account can.
There may be other properties of crytocurrency that make it useful for ransomware, but I doubt there aren't other vehicles that could be used--though alternatives are likely less lucrative due to the overhead in laundering your ransomeware payment into hard currency.