I'm not sure wasn't really possible to postpone this game. Or giving technical defeat 0:3 probably is better than such disgraceful game.
Seems that Belenenses players didn't agreed to enter pplay 2nd half.
EDIT They entered 2nd half with 7 players, another one got "injury" and referee ended game because it's not allowed to play with 6 players.
It's worse than watching fixed game.
Benfica's players could understand such situation with Belenenses team and score 2 or 3 goals but they began this humiliation. they have experienced coach who could tell to stop scoring after 3 goals.