If this were our (Mozilla's) strategy, it's hard to understand why we'd release our code under an open source license, and why we'd insist on every standard we implement being freely implementable by anyone with the requisite chops.

Mozilla "conspires" to do almost exactly the opposite of what you suggest. Having lots of decent browsers available was our old success condition. Now the mobile world is starting to look locked up, so breaking that open to competition and free choice is our new success condition.