Creating a novel, especially an appealing one, is not a simple task, but if it's just about moving a story from one place to another, the difficulty is greatly reduced.
Leonard Ethan didn't plagiarize novels before for a simple reason: after arriving in this world, he obtained the Card System, so he focused all his energy on searching for cultural relics and historic ruins, leaving him little energy for writing.
After all, human energy is limited. Compared to the fame and wealth brought by copying novels, the supernatural powers brought by these cards are obviously more attractive to Leonard.
Not to mention that if he worked hard to excavate various historical sites and antiques, he would have a chance to make enough money. However, no matter how well he wrote, he could never obtain that kind of supernatural ability.