Well laravel uses the application key to generate a password hash. This password has is always unique. So when you run your above code in tinker you always get a different code. However the user can simply login with the same password. When you change your app key you won't be able to decrypt the password anymore, since it's using that key for that.
This article is based on Laravel 4, but should give you an idea on how it works: https://mnshankar.wordpress.com/2014/03/29/laravel-hash-make-explained/