Although the raid and the subsequent criminal investigation were
    carried out in Sweden, the US Government played a major role behind
    the scenes.

As for why the US Gov was willing to act as MPAA's private enforcer...

    (2012) Chris Dodd [MPAA chief] went on Fox News to explicitly threaten
    politicians who accept MPAA campaign donations that they’d better
    pass Hollywood’s favorite legislation… or else:

Trading law for campaign donations is a place one might go after years of trading Gov power for campaign donations.

https://www.techdirt.com/2012/01/20/mpaa-directly-publicly-t...