@chabermaca
in the chapters where they explored Loius's past, they showed that he was adopted with the express intention of inheriting his father's business.
as for our world, certain positions are hereditary, or can also be given via a will.
for example, if someone is the founder of a company and a majority shareholder, they tend to effectively be the head of the company. since those shares are part of their estate, that can be inherited, thus making their heir the head of the company.