This is because the sermons slug is reserved for the sermon post type. You will need to use a different slug for your sermon page’s permalink such as sermon-archive (as in the sample content).
You can see how the slug is used in the URL of a single sermon, such as domain.com/sermons/the-gospel/. If you go directly to domain.com/sermons, it will redirect to your sermons page once you have created it (the page using the Sermons template).
Note: With the Pro Add-on you can change the sermons URL slug to something else. See Settings for Sermons.