Ask HN: How do open source products set product direction?

Working on product teams in companies, its pretty easy to understand how product feature creation and priority is set. Its a mix of customer wants/needs, company directives, and measuring internal priorities. In the decentralized world of an open source product however, there isn't this top down culture to go out and define the thing. How do maintainers or contributors of open source projects decide what features to prioritize or what markets to enter next?