It was against a SIM and it isn't unusual to beat them. In exhibition with GD2 I regularly played the higher Div SIM for one of my 3 ex games. Won most of them. Beating a SIM is not that tough until the upset conditions are met and then wham.
As to forcing them into a Dime. I just won a game where I had 2 DBs and played Nickel the whole way against a better team with a good coach. I had my 3 worst LBs playing in the secondary.