John Kay brings amazing insights in his writings. This article explains why a businessman might not be suited for politics. Simple and lucid.
The most important function of a chief executive is to build a strong and supportive management team. The ability of a political leader to do this is seriously circumscribed, because many others also enjoy democratic legitimacy. They are also elected, and they hold positions of power conferred by their party positions. This leads to dysfunctionality in leadership, as individuals who would not have chosen each other and more or less openly covet each other’s roles must work together: neither Donald Trump nor Paul Ryan would have selected the other for the role each occupies.
Needull in a haystack 
Just what I thought.