They offered higher payments to the providers in the new contract. The providers demanded higher payment, larger increases than what the insurance companies were offering. Let's think logically in terms of who might be the bad guy.
Insurance does not create medical costs, they merely pass on costs created by medical providers. UHC offered to pay Piedmont more than they are currently paying and Piedmont said no, they wanted even more. Is Piedmont currently operating at a loss, such that the increase offered will not permit them to continue? Why are they demanding an even greater increase than what the insurance company is offering?
Piedmont's costs have increased? Okay, what costs? Minimum wage has increased has it? Nope, not in Georgia. There is a movement afoot to do that, but the movement has barely started and employers cannot base prices on something that has not happened yet and may not happen at all. With inflation at barely over 1% and and producer prices flat, why do medical providers need price increases at all?
As to the "for profit" picture, Piedmont is "doctor owned" and does not publicly report finances, but similar hospital groups typically operate at 35% to 50% profit margins. Meanwhile United Healthcare is operating as of June 2016 at a 6.3% profit margin, which is hardly unreasonable.