Four years ago, Robert Kyncl, YouTube’s business lead, confessed a mistake. "I thought that YouTube was like TV. But it isn’t," he said at Google’s annual advertising show. "YouTube talks back. It’s interactive. And YouTube is everywhere." Kyncl’s message resonated with advertisers. Gross ad revenue at YouTube soared from roughly $4 billion in 2013 to $11 billion last year, brokerage firm Monness Crespi Hardt & Co. estimates. At the same event in 2016, Chief Executive Officer Susan Wojcicki boasted about taking ad dollars from traditional TV networks.