The Russians have shown themselves capable of surveillance in places we don't expect. They're also good at it. That assumes of course that they had a bug wherever Ryan, McCarthy and McMullin et. al. had their conversation. They probably didn't. Maybe someone had a pearlcorder going, or their iphone on or whatever. Maybe the Russians had someone's phone compromised using NSA tools, or tools of their own. Maybe someone had that recording in their files and the Russians hacked them. None of these are a reaching.
Occam's Razor on the Russian hacking was not to instill a puppet, but to maximize chaos within the federal government. Now that it starts to look like they've gotten all the mileage they can out of Trump, it's time to start new fun.
This one kinda speaks for itself.
I am not saying that of course the Russians did this. I'm saying that it could be the Russians, because they definitely benefit from all this.