It's clear it was nobody's interest to leak this call. Trump wants it to be confidential, obviously, and Raffensperger too because he sounds incoherent and scared.
Obvious conclusion: the call was leaked by a third party who eavesdropped to send a message to Raffensperger he's being eavesdropped, and if he had made any agreements with Trump, they would know it before Trump can protect him.
It could have been leaked by military ops white hats to show him they’ve been listening to him the whole time as well... but this seems more unlikely because it went to the WaPo.
Likely black hats..