A reason why it can be a YSK is because the native people of the great turtle island remembered the creature when it came back. It spread so fast because everyone had a cultural remembrance of them and was able to remember stories about them to tame and ride them. Much of the history taught to Americans is that the natives were primitives and lacked a rich history. Many stories that were passed on from elder to youth were done in literal languages and deviation from the story was not to be done.
The tribes have lots of other stories that are told from time forever and those stories should be more well known. Many times in the past people didn’t listen to the tribal knowledge and nature can be deadly if you don’t understand the motions of say a river