You nailed it. Smart students know that a class worth taking will require work, he didn’t provide that.
When I was in kollege, a course like that was known as a “gut course”, meaning that there was little work involved, and an “A” was all but guaranteed. For example, there was a survey course in geology that was known as “rocks for jocks”, and an astronomy course known as “stars 1”. That was a little known course, but the word got around and to the surprise of the professor, suddenly hundreds signed up for it. They had to move it from a classroom to a huge lecture hall.