The Browns defense is not great. It is not good either. It has been a "bend but don't break" defense this year. And it has. In two of the Browns' wins, the defense iced the game with an interception.
And in the last two wins, against the Rams and Seahawks, in two occasions in each game, the Browns defense held on 4th and 1. Four times in two big wins, when it mattered most, they held on.