Option 1 - someone dropped probably a few million miles on booking multiple seats on dozens of dates just in case they want to fly one of those dates for 'free' (in economy!)

Option 2 - The airline realized they had accidently release award seats on a new route where they hadn't intended to and removed them.

Sure, I guess option 1 is possible, but my money would be on option 2. One way or another United isn't going to care what happened. If it truly was option 1 then NH might be interested, but odds are they already have systems in place to detect such abuse if that really is what happened.