There are a few main categories of approaches to creating static sites based on Drupal data.
Projects like Tome are Drupal projects that provide an option to export a static version of the site..
Generic Drupal Export
Custom code can be used to export data from Drupal into formats like Markdown, JSON, or CSV which can then be used with many static site generators. See Drupal Serialization Step-by-Step as an example. Tome can also be used to export Drupal data as JSON for use with other static site generators.