It was not that hard to guess that the main impetus behind the FRA law and the capability to spy on the Russians' Internet traffic was the prospect of trading any valuable pieces of intel with friendly major powers, apparently specifically the US. In retrospect it occurs to me that the Americans might actually have been actively lobbying for the law in the first place.
Yes I agree this is very likely. FRA has certainly provided much valuable intel in the past from radio analysis and for the cooperation to continue it felt the need to listen into cabled communication as well.