First point, Feynman joked about his IQ being 124. It was not. His IQ was tested with the quotient method which is no longer the standard method. Anyone who has read or heard about his work with QED would understand that it's brilliant.
Secondly, the statistics you are using are for the general psychology graduates. The general graduate does not go on to lecture at Harvard and obtain tenure at U of T. Peterson reports his IQ to be 145.
Third, if Feynman did have an IQ of 125, and produced as brilliant work as he did, then it would be more than possible for the average psychology graduate to produce brilliant work with the "same" IQ.
Also, an IQ of 125 is almost 2 stds above average which I would consider somewhat bright. Especially, if you truly believe Richard Feynman had an IQ of 124.