React is javascript, so it needs a javascript engine in order to run, so one way to see a laravel project is to think of it as the 'backend' api server, which is completely separated from the 'frontend' server which uses node to run the javascript part of the application.
In other words, you have two apps, the one with laravel that exposes an api which could be used by any other service in the infrastructure, and the reactjs app which is a nodejs app that consumes that api, and handles the magic of react + redux.
The way your site is actually accessed from the outside world is thru the express/nodejs app, which calls the laravel api for data persistence and other business logic.
The laravel app handles sessions, oauth, the database, file access to the hardrive and so on, while the nodejs app handles the actual website routing, the templates, the css and javascript part.