The Cleveland Browns of the late 1970s early 1980s were called the Cardiac Kids for a good reason. They trailed late in games a lot and many times by two scores and would have to either score once very quickly to win, or have to score twice with like five minutes left in the game.
The Browns defense was not horrible and perhaps not even bad, but certainly not dominant which is what it became under Marty Shottenheimer in the mid and late 1980s. And as a result they would get into shootouts and when they play good teams with good defenses, would fall behind late and have to make great comebacks to win.
The 1980 Raiders were a very good if not great all around football team. That could score a lot of points and simply shut teams downs. As they did in the AFC Playoffs and in the Super Bowl that season. The Browns were simply beaten by a better all around football team.