I suppose entitling your video "ATC doing their job" doesn't have quite the same ring to it.
There are a few controllers who frequent this forum, I'm sure one will be along shortly to give you a definitive answer.
In the meantime, if you click on "Show More" on the video page, you will see the statement "According to an air traffic control planes can use the same runway if the departing plane is airborne before the arriving plane touches down", though I suspect the correct answer is more about when an approaching aircraft can be given a landing clearance.