Office of National Statistics (ONS) figures show a strong correlation between having a degree and being wealthy. However, 'correlation' does not prove 'causation'. i.e. just because two things happen together doesn't prove that they actually cause each other. Daffodils bloom in spring before tulips, but blooming daffodils aren't the reason why tulips bloom.
A degree doesn't cause wealth. Those who have the discipline to work hard academically to get a degree are more likely to have the discipline to work hard in their career to get wealthy. The key common factor is having the discipline and the work ethic.