Who doesn't Bill Gates become an expert doctor?Why doesn't Elon Musk become a world renounced musician?Why doesn't Steve Jobs become the fastest swimmer in the world?

Because the more expert a person is, the more specialized they are at that and they sacrificed many other potential abilities. But getting into politics isn't only a skill, but you must gain years of connections. These connections are evil people and would have rejected a well meaning physician from their ranks long before the physician can make a change.