Laravel may seem like a monolithic framework because it includes features for building almost any kind of web application. Under the hood, though, Laravel is a collection of many separate modules, some developed as part of the Laravel project and some from third-party authors. Part of what makes Laravel great is its careful curation and seamless connection of these constituent modules.
Since Laravel version 5.3, Vue.js has been the default frontend framework included in a Laravel installation. There's no official reason why Vue was chosen over other worthy options, such as React, but my guess is that it's because Vue and Laravel share the same philosophy: simplicity and an emphasis on the developer experience.