I'm not convinced it's their ultimate goal, or even one of their goals at all, since poor implementations could water down their branding. But it is definitely a side effect.

That's a very cynical view. I think their ultimate goal is getting nice looking and functioning apps on their platform.

Material is an Interaction Design play first, a design play second and maaaaybe a branding play third but whatever. If it makes apps and the web a better place because every Joe Schmoe dev can focus on functionality instead of design (which a lot of people simply suck at) that's great.

But also not strictly on their platform. There's top-down "encouragement" from management to use Material Design in all their iOS apps too, which isn't really being a good citizen of the platform.