While Richardson is averaging 3.5 yards per carry, it's not like there was much talent around him that stretched the field. Defenses could put 7 and 8 guys up front to stop him.
With the Colts, defenses have a much better passing game that they have to defend, which can open up more holes for him.
That's why the trade is mind boggling to me.
Only plus for the Browns is this; They now have 6 picks in the first 3 rounds next year to get a good quarterback, in what should be an extremely deep draft for QBs (Bridgewater, Mariota, Hundley, Boyd, Murray, Manziel, McCarron).