When your defense gives up 300 yards in the first half, which includes 157 yards receiving by Roddy White, the score isn't going to favor you. When the Falcons record 110 yards rushing in the first half, which includes 87 yards rushing by Michael Turner, the score isn't going to favor you.
When your franchise quarterback completes only 11 of 20 passes for 95 yards passing in the first half, the score isn't going to favor you. When your starting wide receiver decided that all he needed was an attitude adjustment, rather than working over the bye week with his starting quarterback, and has 25 yards receiving on three catches to answer in the first half, the score isn't going to favor you.
When you only kick a single field goal in the first half on five offensive possessions, and when the opponent scores three touchdowns and a field goal on five offensive possessions, the score isn't just unfavorable, it's disastrous.
Whatever could go wrong for the Bengals in the first half, went wrong.