Being a lawyer can be regarded as a kind of dependence on professional skills, because lawyers need legal knowledge and professional skills to provide legal services to others and earn remuneration. Although the legal profession also includes some administrative, auxiliary and clerical jobs, these positions are generally not considered as "relying on professional skills".
Generally speaking, "getting rich by professional skills" in the eight characters refers to working with specific professional skills to obtain wealth. Being a lawyer can be regarded as one of the representatives of this kind of profession.