For several years installation of a new version of Movie Studio has automatically uninstalled its immediately preceding version. It is not a policy with which many users agree but it is the company’s policy.
To add to @emmrecs comment, the replacement of older software by newer versions is not restricted to Magix products and is a common feature of many other software producers.
This is usually done to avoid version conflicts as new features and processes are added to software to cater for more modern hardware and capabilities.