Aging media mogul Sumner Redstone stepped down as executive chairman of Viacom on Thursday and was replaced by CEO Philippe Dauman, a move that immediately disappointed investors.
Although the decision mimicked a similar move at sister company CBS, Thursday's action has the potential to set off a future board fight. Redstone's daughter Shari said Wednesday she was against Dauman's promotion to the role because of his deep involvement in Redstone family affairs.
Investment adviser SpringOwl, which holds a stake of undisclosed size in Viacom, had also opposed Dauman's bid for the chairmanship, calling instead for an independent director.
Dauman is one of seven...