Money | Twitter Twitter CEO Evan Williams Steps Down, COO Promoted Dick Costolo will head day-to-day operations By Nick McMaster Posted Oct 4, 2010 4:31 PM CDT Copied Dick Costolo, chief operating officer at Twitter, speaks during his keynote presentation at the Ad Age Digital Conference in New York, Tuesday April 13, 2010. (AP) Twitter co-founder and CEO Evan Williams is relinquishing leadership of the microblogging site to COO Dick Costolo, reports the Wall Street Journal. "Building things is my passion," Williams offers as explanation for the move, adding that he asked Colstolo to take over. Adds Costolo, recently "it became clear to everybody that Ev's got to be able to focus on product strategy." The move also comes as Twitter looks to reap some sort of profitability out of its explosive growth. Read These Next Saudi tells Iran to wise up, 'stop attacking their neighbors.' Ex-counterterror official Joe Kent is under investigation by the FBI. Trump cracked a Pearl Harbor joke with Japan's leader. Navy's most advanced aircraft carrier pulls out of the Iran war. Report an error