I think like any other topic. You write articles about it. People looking for experts in the topic find your articles, keep your name in mind, and then contact and hire you as a consultant when needed. You get invited to speak at conferences, etc.

Conversely, if you’re looking for a job in this line of business, you can add your articles as references. They’re (additional) proof of knowledge. Maybe there’s a special angle you bring to the topic.

Online is a door opener for the offline business.