Seems like the async on the script tag was the issue. It only loaded after a link was clicked.
If I click on any link and go back to the page with the map on, it renders.
I get this
<script src="https://maps.googleapis.com/maps/api/js?key=<%= Rails.application.credentials.dig(:google, :google_maps_api_key) %>&libraries=places&callback=initMap" async defer data-turbolinks-eval="false"></script>
What am I missing?