There was no salary cap then and Curvin Richards was a nothing player.
"Do you think I would've cut Troy Aikman? Of course not." - Jimmy Johnson
There is much more to it than that. Jimmy was nuts about that Washington loss two weeks before. Dallas lost because aikman, emmitt and Irvin all had key fumbles in the game. Aikmans in the clutch moment late in the 4th quarter ( today it would be the tuck rule and Dallas would not have lost the ball or the game)
Anyway jimmy went crazy on the plane ride home and worked the team to death before the Atlanta and Chicago games to finish the season.
He was looking to drive home the point about turning the ball over, I believe he even warned Richards to not fumble the ball when he went in.
People never account for the rest of the story when they bring this jimmy stuff up. It all had purpose