The Group C match, which sent the Greeks into the last 16 of the Champions League, was controversial as Anderlecht had three men sent off - Chiekhou Kouyate, Fabrice N'Sakala and goalkeeper Silvio Proto - as well as conceding three penalties, two of which were saved by Proto.
And Van den Brom, whose side were already out of the competition, claimed that he knew from the outset that they would struggle in Athens.
"Let us start at the beginning - it was soon clear to me that we could not win this match," he said.
"Were all the decisions of this man [referee Wolfgang Stark] wrong? Yes.
"I also hear that it was the last Champions League match of the referee. Well, then I'm happy for the other teams in the Champions League. This was just outrageous.
"Anyway, I'm still happy with what my players brought despite all the adversity. They continued to look for more. We still believed thanks to two penalty saves.
"Overall, this has just become a disappointing campaign."Javier Saviola scored twice as Olympiakos booked their place in the knockout phase at the expense of Benfica.