Other mistake: When Captain Hernandez gives an order to her helmsman, she says "lieutenant". But the helmsman has only one pip on her uniform, she's an ensign, not a lieutenant.
Factual error: In a cutscene showing Enterprise in orbit around Earth, the Great Lakes can be seen below. The video is reversed left-to-right. (00:08:40)
Answer: While ratings did drop, there was a lot going on to cause the rating drops and cancellation. First, "Enterprise" was on UPN, which was dissolved a year after the show was cancelled. At the time of cancellation, it was UPN's highest rated drama. Because they were on at night, they were often preempted by local UPN broadcast of baseball games. And it wasn't even aired in every market. They also lost a major corporate backer early and it was difficult for them to over come that loss. Plus, for season 4, they switched to a Friday night line up, so they were competing against Fox shows, like "The Simpsons" whereas on Wednesdays they didn't have much competition.
Bishop73