I'm surprised that you didn't reject it for plagiarism. That's what I did when I discovered plagiarism while reviewing a paper. I wasn't an expert in some of th

I'm surprised that you didn't reject it for plagiarism. That's what I did when I discovered plagiarism while reviewing a paper. I wasn't an expert in some of the background material, and they referenced a survey paper on that topic, so I went and read that survey paper. To my surprise, the author had lifted entire paragraphs from the survey paper. I rejected it for that. I was actually a sub-reviewer, so I notified the PC member who had asked me to review the paper, and they agreed that yielded an automatic rejection.