A more interesting question is, who is paying the Swedes, and how? They really don't have a dog in this fight, so whatever motivation they have, it hasn't been made public. Yet.
Really?
"The Pirate Bay (commonly abbreviated TPB) is a Swedish file-sharing website founded in 2003..." - https://en.wikipedia.org/wiki/The_Pirate_Bay
There are media companies in other parts of the world too you know. The world is a big place, it even exists outside the US.
As for the motives... IF the arrest of Anakata was a paid job, what other reasons than keeping good relations with the U.S. do we (or rather, the Swedish state) need?