A mediator is needed to reconcile men to God because of mankind's sinfulness. The Bible clearly demands a mediator.
However, if a POOR man was selected as mediator, it's likely to go against those who are rich.
On the other hand, if a RICH man was selected as mediator, it would likely go against those who are poor.
What if it were possible to find a RICH man and a POOR man? Now, we got a qualifier to serve as unbiased, righteous mediator!
2 Corinthians 8:9 For ye know the grace of our Lord Jesus Christ, that, though he was rich, yet for your sakes he became poor, that ye through his poverty might be rich.
With one pierced hand, the Lord Jesus Christ takes hold of His throne, and all the heavenly riches associated with it. With His other pierced hand of grace, He reaches down to rescue sin-sick, poverty-stricken sinners.
This is the absolute majesty of what God does as the ONE MEDIATOR!