Wire and bank fraud occurring in the U.S., according to the report.
It's also a bit unfair to lay any credit/blame on Lynch for this one - it's a multi-year investigation. I suspect the timing of the arrests and announcements might have something to do with the upcoming FIFA elections, as the U.S. government and soccer officials are both of the (correct) opinion that Sepp Blatter and his cronies need to go.
Frankly corruption is sports is BAD across the board, not just in FIFA. The IOC does come to mind.
Am reading some EU news outlets, and they seem to think that its also due to Russia having been awarded the 2018. US State Dept. lobbied FIFA hard to rescind the award, but they did not.