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.
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.