If we take any dissertation, it is basically regurgitating the knowledge of other people. Indeed, you have to cite other people. It is a requirement. So it is understandable that some academics at times use other people's work and forget to properly cite those original authors. And surely with AI this problem will become more common. I guess the problem arises when people like Arday systematically pass of other people's work as their own on a grand scale, without giving proper citation. It is perfectly possible to commit plagiarism by mistake, but if you do it on the scale Arday did, then it becomes a different issue. As you rightly said he also claimed to be affiliated with other institutions and that was not the case. The quantity of his lying was over the top.