Stealing personal information from the tax authority for years? I consider that rather serious.

Not on the level of killing someone or some such of course but in terms of potential damage to many it ranks rather highly.

Ah yes, the things he hasn't been charged with yet?

I agree that they do count as serious though.

That's how the Swedish court system works, he has been accused (with the higher level of confidence if I remember correctly) and won't get formally charged until it is taken up in court. The system is a bit different compared to for example USA.

He was taken into custody while the investigation was being finished up.

Ah yes, that's ringing a bell (I think from the whole Assange debacle). Makes the reporting in torrentfreak guilty of some rather dishonest spin doesn't it?