Below is an excerpt from a book.
I’m a man who loves traveling by myself. On every vacation in university, I spent about 7 to 10 days as a backpacker, traveling around China. Since it was self-guiding tours, no guide would come to help me arrange anything.
As I understand, self-guiding tours is a plural form so it should be Since it were self-guiding tours. Is my understanding correct? Or should it be changed to Since they were self-guiding tours? Which one is correct?