Pinterest Is a Unicorn. It Just Doesn’t Act Like One.

The company’s growth exploded by 2011, just a year after its service went live, spawning countless copycats — for families, for music, for pornography, for Lady Gaga fans — and clones in every major country. It seemed possible that Pinterest could be as successful as Facebook, Instagram, Twitter or YouTube — maybe even Google. The market for social media advertising was still young and up for grabs. A Forbes cover story about Pinterest declared, “Move over, Zuck.”

The business case was simple and powerful: It was a shopping mall disguised as a mood board that held its users’ aspirations, unearthing pure and unfiltered commercial desire. “You can draw a direct line from those interests to a commercial opportunity or retail category,” said Andrew Lipsman, an analyst at eMarketer.

But just as the company began selling ads in 2014, user growth stalled and it wasn’t clear why, according to multiple people familiar with the company. The company disagreed that growth had stalled, arguing that it had “slightly slowed.”

Executives on Pinterest’s “growth” team proposed spending $50 million a year to acquire users through marketing, a common tactic for web companies. Other executives argued that the company should court celebrities and pay influencers to share content on Pinterest, similar to YouTube’s premium content program.

Mr. Silbermann opposed both, according to people familiar with the decision. He preferred what he called “quality growth.”

“There’s a natural rate at which you can scale a company that’s healthy,” Mr. Silbermann said. So Pinterest stuck to its knitting.

Not everyone was sold on the message. Even by the standards of start-ups, where employee turnover is common, the number of executives leaving Pinterest has been notable in recent years. Since 2015, the company lost people who ran media partnerships, operations, finance, growth, engineering, brand, product, tech partnerships, marketing, corporate development, communications and customer strategy, along with its general counsel and president. Jamie Favazza, a Pinterest spokeswoman, said, “Turnover is natural at high-growth start-ups, but we’ve built a strong team of leaders for the long-term.”