Fair play to them because it's quite the fairytale. It's not like they spent a ton of money to manage it. Certainly the team they beat tonight (PAOK) are a significantly bigger and richer club.
In fact I just looked and of the team that started tonight, eight of them played for Ostersunds in the Superettan (second tier), including Fred. Of the ones that didn't, two of them were signed from other teams in Superettan. Only one player was anywhere near established in the top flight when he signed, Tom Petterson (the only ethnic Swede in the lineup), who was a squad player at IFK and previously played for Belgian no-marks OH Leuven.
This is broadly what DDF had in mind when he was signing the likes of Dean Keenan and saying "the boys" deserved a chance to prove themselves at a higher level, but unfortunately instead of signing a bunch of hard-working professionals who were drilled to punch significantly above their weight, he instead lumbered the club with a job lot of gurning tossers who played naked table tennis when they weren't getting drunk and injuring themselves. Sad!