At last year’s Association of National Advertisers (ANA) conference, in an interview, former P&G CMO talks about how ANA became successful and the importance of having an ambitious purpose: 

The ANA has had explosive growth since 2001, 2002. And the reason I think is actually because Bob doubled down on their purpose and their ideal with this organization.
They kind of got very explicit they want to be the leadership voice for the industry. And to be a thought leader versus a run-of-the-mill trade association. So they really internalized that, activated it, and the way he kind of brought that to life is that he formed a great board.
And his principles for the board was, you just can’t come on to this board to show up, you have to do something. You have to be actively involved. You have to lead something.
A great board, with a plan, and a really powerful purpose, and now can we imagine life without the ANA? I think it’s been an extraordinary story, and Bob Liodice gets a tremendous amount of credit, and his team. I think it’s a largely untold story.

And on the importance of an ambitious purpose:

I’ve learned over the past several years that there is a difference between brands who have a purpose or an ideal, and those who have a really ambitious purpose. And to me, the ones that have an ambitious purpose transcend their category. They really have an innovation strategy, a plan, a profile that is really disruptive.
You look at what Google is doing. We use this has an example a lot. They have an ambitious purpose. And they’re constantly innovating like crazy in unexpected ways to bring them to life.
I think brands are trying to make a meaningful difference in their category are great. And if they’re able to activate that purpose in all they do, they’ll have a good business.
The ones that really think beyond that like Dove, which is an example we often use, they go way outside their category. They have been wildly successful, and they have attracted a lot of consumers and a lot of talent by the way also on the brand. Because they have an ambitious purpose.

And on why having a stated purpose is not enough:

I think it’s very possible for a brand to have a strong ideal and still not grow. What usually happens in that circumstance is the ideal is not activated with employees.
And often companies have a great website, a great stated purpose, but the day-to-day work of people doesn’t change.
So on paper, someone can look really good, it’s really about the daily behaviors. And it’s about how work changes for all employees, and about integrating the purpose with the business.
Lot of people say we have purpose, but we also have to run the business. That doesn’t work. 
So to me, a strong ideal, activate it, will work. A strong ideal, moderately activated, will be ok, but what happens is that it develops a lot of cynicism with your employees.
So it’s really about coherence to the ideal, day to day behavior, and if that’s not there, you can have a really powerful ideal, but it would be flat, it won’t grow the business.

Link to the source with the video of interview is here.