You have installed AutoCAD on Windows operating system. Your network administrator temporarily allowed local admin rights to do the installation, after which your network local admin rights were removed (policy of the network administrator).
Autodesk product installation typically has two stages:
The first stage is when the program (AutoCAD, AutoCAD Civil 3D, AutoCAD Architecture, etc.) is being installed.
The second stage is when a Windows user starts the program (this is called the secondary installer, which creates Windows user-specific registry keys and file/folder content for the product).
For both stages to work properly the program needs to be installed and at least started by the user with admin rights. Once the secondary installer completes its job, and you verify that the program is working fine, you can revoke admin rights from the user account.
For program updates/service packs, you would also need admin rights to install them successfully. Typically most users on their local workstations are granted local admin rights for this.