The Iraq war was all about oil

That's what the left and anti war groups keep telling the world. How do they explain this?

"BP and CNPC have won the right to help Iraq develop the Rumaila field. The UK and Chinese companies beat ExxonMobil, the US oil company, which had partnered with Petronas, the Malaysian oil company. BP clinched the contract when it agreed to reduce its fee per barrel from $3.99 to $2."