Former Viacom executive joined the network in 2012
Chairman Bob Greenblatt notified colleagues on Tuesday via email, promising: "I did everything I could to keep him here"
Groom began as an NBC page in 2003
"What we're trying to do is bring quality, must-see TV back," Jennifer Salke, president of NBC Entertainment and Universal Television, told TheGrill
Hiring Brandon Riegg away from ABC was a first step in finding reality programming to compete with "American Idol"
On the competition: "If I could change anything, it would be to disconnect cable"
More sage wisdom for small screen sizzlemakers, including Steve McPherson, Dawn Ostroff and Angela Bromstad
Angela Bromstad: "There's tremendous continuity and calm. We're moving in the right direction."