Eureka Seven aired when they had no money and few options, and Soul Eater isn't much different.
They could pick up Ushio & Tora, but it will have zero name recognition, a non-standard artstyle, and will be longer than any of it's competition for the slot, which means it's a bigger deal if it fails.
Have you even seen Ushio and Tora? This thing feels like it was genetically engineered to be on Toonami.