It all started back in the early 80's when the maker of Cabbage Patch kids were an actual hot seller. Toy companies looked on in awe at the lengths parents would go to get a toy for their child. From that point on there have been lists of the hot toys to get and dutifully parents go out and get those toys. It turns out that much like the lists of top steak houses you see in airline magazines the lists are paid for in the form of kickbacks to toy stores. The higher the kickback the more a toy store will talk your product up when the local news shows up. The parents see the report on television and think their kid must want the toy. Some parents talk to their kids about it and that leads to other kids talking about it at school and asking their parents for the toy because they want to be the same as Frankie.
The reality is that none of the top toys in demand for Christmas on these lists comes close to the top ten in sales of toys but what it does is get them noticed and sold and makes the manufacturer get a little more room on the shelves the next year.