I don't know about any industry standards, but the best experience I've had with internal documentation was in an organization that had a dedicated team responsible for supporting and curating the documentation infrastrucure. But they were not responsible for writing all of the documentation themselves.
The system they used happened to be a wiki, but any single source of truth should work. I'd go so far as to say it should natively support versioning. There's nothing I can't stand more that people emailing around Word docs with multiple pages dedicated to a document changelog. If you need a copy of the current revision, it should be easy enough to export from the source as a PDF.
Most of the team had a tech writing background. They were responsible for developing templates for common documentation types. They'd help other teams get started writing their own docs. They'd audit the docs people were creating and potentially edit them for style/consistency. It was glorious.
And let's be honest, writing good documentation takes time and effort. There's no magic tool that makes it easy. The SMEs of a given system must be willing to write (and keep updated) documentation for their various systems/projects.