Here's why:
* Inorganic chemistry focuses on the study of all chemical compounds except those containing carbon-hydrogen bonds (which are the domain of organic chemistry). Oxygen is a fundamental element and forms a wide variety of inorganic compounds.
* Inorganic chemists are experts in the reactivity, structure, and bonding of inorganic substances, making them well-equipped to describe oxygen's chemical properties.
While other types of chemists could also contribute to understanding oxygen, inorganic chemistry is the primary field associated with its fundamental chemical characteristics.