This line contradicts with others. My issue is that Google tries too much to enter new markets. Google is fine with starting 10 projects if one of them will be successful and kill others. It is the same thing you wrote.
The distinction is in having a sustained effort behind the project. One may have 6 messengers while none of them gets the resources to succeed. The projects are used for a short-term career advancement, not for a long-term effort to open a new market.
The logic is indeed to have "... 10 projects if one of them will be successful and kill others". It just does not work that way. Google's leadership (the top ~10 people) position themselves above the fight. They don't throw their weight behind one of the (for example) messengers because if it fails it's their failure too (remember Google +?). As a result the users are confused, the resources are spread thin, and none of the 10 wins the market.