If you drop a dangling slinky, you would expect it to just fall to the ground but that is not what happens. What actually happens is that the bottom just hovers for a moment until the top collapses on top of it as seem in the video There are two main reasons why this occurs.
This first has to do with newtons law of action reaction. As top falls the spring of the slinky is pulls it down faster the pull of gravity. At the same time the spring is pulling the bottom up countering the pull of gravity. As a result the bottom remains suspended until the top collapses on to it ending the action reaction effect.
The second is that because the bottom of the slinky is held up by tension and it take the time needed for the top to collapse for the bottom to get the message that the top was dropped.