It's thought that it's Russian illegal agents doing this. A lot of them locals recruited online. Really cheap ops done by really cheap people, using cheap and deniable gear.
It makes sense. In the Netherlands, young people (<18) have been recruited for all kinds of stuff by organized crime; bank account money muling as part of laundering operations, laying bombs, getting drugs / other smuggled stuff out of shipping containers in ports, that kind of thing. They target these because for them, a few hundred € is a huge sum, and the legal system is very forgiving to underage people, assuming they even get caught.