It turns out that the software used in VFX rendering is pretty darn expensive. Licenses of RenderMan, for example, were several thousand dollars a node (RenderMan just lowered their prices, it's true). Nuke, Maya, and other tools were similarly expensive.
The companies that created the software typically wouldn't consider licensing on shorter terms than six months; which made scaling up for a big movie very expensive. Zync managed to negotiate deals that would allow them to license software on an hourly basis. That is their real innovation.