A very good illustration for newbies.
Sway can occur any for any rig. Newbies, in particular, do not understand the importance of having a suitably heavy TV, so we see perpetual posts such as, is my truck enough?
To bring sway under control, the lesson is to apply the trailer brakes only. This underscores the importance of having a trailer brake controller in ALL tow vehicles. IMHO, this should be a vehicle licensing endorsement issue.