The biggest projects span such a wide number of teams and/or departments and/or product areas (product areas at Google are headed by Senior VP's) that you're never going to have someone with the formal authority having either the time or the technical knowledge to run those projects. Even at the department level, the VP will have hundreds or thousands of people reporting to her, and so she's not going to have the time or attention either.

So the authority gets delegated down to the technical leaders, and while it can happen that there will be conflicts that have to be escalated to the VP or SVP level, it's usually because a team simply doesn't have bandwidth to satisfy a request, or are being given conflicting signals as to the prioritization of different projects, and so we need to escalate to senior management to either get more head count, or agreement that a given prioritization will mean that the project will slip, etc.

The technical leaders make the technical decisions, and are responsible for the technical decisions. Management makes the resourcing decisions, and product managers make the product decisions. Usually, it's pretty obvious whose domain a particular decision is in, and as a senior technical leader, I actually know enough about the constraints that I can tee up the question, with the tradeoffs, and then say, "but that's a product-level decision: do we ship with now, or do we slip and so we can add this particular critical feature? Note to management: if you don't like the velocity of the development, we badly need at least 3 more head count by next quarter or we will be presenting you with more Hobson's choices like this."

And that's fine with me; I don't find working with recruiters and negotiating with the CFO for headcount, or sitting in an all day meeting trying to divide up the headcount granted to the department to the various teams. Not having to do that is not "lacking muscle", it's being freed from work that I don't like to do.