What just happened?

The process we went through results in the whole Qt infrastructure appearing on your disk. You can examine the directory you pointed to the installer to see that it created a number of subdirectories in this directory, one for each version of Qt chosen with the installer, and another one called Tools that contains Qt Creator. The Qt directory also contains a MaintenanceTool executable, which allows you to add, remove, and update the installed components. The directory structure ensures that if you ever decide to install another version of Qt, it will not conflict with your existing installation. Furthermore, for each version, you can have a number of platform subdirectories that contain the actual Qt installations for particular platforms.