Nice to see Knoppix featured here. This is basically the distro that pioneered the "Live CD" Linux where you can play with the full system without the need to commit to a full install. This was huge at a time where it was quite difficult for a non-technical user to install Linux. In addition, it was based on Debian, which at the time still was much more difficult to install than now, so for many people Knoppix was a way to use Debian without having to use that old installer. To top that, it used KDE.

Since then, a lot of Live Linux distros emerged, with various features offered; Debian got a much better installer; and then Knoppix dropped KDE Plasma as their desktop environment. All of that made me to move over to better "Live Linux" distros.