That extra $5 Million is the expected cost of Federal Monitoring of the PD. Reports, extra personnel to generate them, etc. You're right, they should have been doing it right all along but just remember, it's Seattle PD. I had some experience with their Command Staff back in the 60's while working for a Seattle Company. That was back when the "Envelopes" were passed around from patrolman to chief, everyone taking their share from the cash in it until it made it to the top.
What's really changed?
Best thing that could happen to SPD is to be under DOJ's supervision. They'll fight it like hell and claim all the extra costs will hurt. Instead they'll just end up paying settlements for the misbehavior of their officers. I hope DOJ doesn't buy the BS the Mayor and Chief are putting out with their 20-20 "plan".