So that they can increase their own pay and benefits. Nonprofits still have to pay their staff and the amount of money some pay theirs can be rather... inflated.
The operating surplus says nothing about how they increased pay, except that they increased revenue more than they increased pay.
If you wanted to justify further pay increases this would be the best strategy - if you have an operating deficit you'll be under pressure to cut staff or pay.
Again I'm being very cynical here and I have no idea if this is actually happening. Just speculation.