My point wasn't using an existing affiliate network versus bulding one. Was having the skills to spread malware and using an affiliate network to get the malware, versus having the skills to spread malware and coding your own malware. But ok I got your main idea.
Yes, the creators of the malware could also run the network. But they would spread wider by paying a bounty for each ransom, based on through whom the targeted system got infected.
The benefits are that the creators get more people to hero then spread their blackmail.
Call it affiliate, call it MLM, call it resellers, call it a distributed crime syndicate. Same thing.