The developers put a simple system into production early, and update it frequently on a very short cycle. This makes the software ‘visible’ to the Product Owner and Stakeholders, and is a much better indicator of concrete progress that updating a project plan. It also gived the Product Owner the opportunity to use the system much earlier than would be possible under traditional processes. As such, the Product Owner sees returns on their investment in the system much sooner.
Releasing early and often gives the Product Owner a better opportunity to steer the project, accommodating change as required and putting the project back on track if it is deviating from the Release Plan or Iteration Plan. This is a very powerful risk mitigation strategy, allowing the system to adapt to changing business requirements.
Note that releasing the software to the Product Owner doesn’t necessarily mean that it will be deployed to production. That is completely up to the Product Owner, and is subject to all of the scheduling, certification and deployment issues typical of any other software development project.