Hardware makers support Google OS

Google is a cohesive force between these makers that might not otherwise have existed, except tenuously. Sure, they could have formed an industry consortium, but maybe a direct partnership never suited their game style. Maybe it's easier to band together indirectly.

It doesn't hurt that it's all under a brand name that's arguably a lot better than anything they could have come up with individually or (heh!) as a committee.

Quid pro quo?

Perhaps they fancy being partnered with Google?