Your examples of successful forks are due to branding amongst technologists, who understand the concept of a fork and who were following the most-trusted of the descendents (another example being Hudson and Jenkins).

Consumer brands are not as easy to fork. If Coca-Cola opensourced their recipe and then faced a fork by Examplesucre, I don't think anyone will really be betting against Coke.

Similarly, the longevity of mainline integrity for Linux relies heavily on the fact that it is a trademark and that the trademark holder (Linus) is trusted with it. Fork Linux as much as you please, basically nobody will care.

Google's power over Chromium comes from its power over Chrome. If you don't think that's true, fork it yourself and prove us all wrong.