1. Frats select for lower overall academic ability. Few physics, biochem, ee majors. This bleeds over into their easier major.
2. Frats select for larger physical stature and attractiveness. This deselects for academic performance and strongly selects for business success.
3. Most importantly, there is little artistic, creative, or purely intellectual emphasis here. If a young person is dedicated to "going for the money" at an early age, the results are not surprising.
These advantages, while enduring, are likely to reduce with time, in my opinion.