I would have probably given this episode of The American Experience a higher rating, but I recently viewed a far better documentary on the subject that is only 40 minutes in length. There are no survivor accounts in that one, probably because it was made in 2018 and this episode was made in 1998 when there were still some survivors alive plus I think there is some stock footage of older interviews included.
Because there are many intimate accounts of some people who were actually sick and survived and other accounts of those who were children and lost friends or sometimes parents, there is not that much room in this episodes for the whys and hows. For example, this episode talks about how bad the outbreak was in Philadelphia. Why? The 40 minute documentary I reference said that a War Bond Drive parade was scheduled in Philadelphia when there were only a few flu cases. The public health officials begged the mayor to call off the parade, but he listened to the chamber of commerce instead and thus the few cases spread to the many with over twenty thousand people ultimately dying there, bodies lying in gutters, coffins being at first guarded at gunpoint so they would not be stolen, and then finally mass graves when the coffin supply was exhausted.
I'd recommend you see both documentaries if you have the opportunity. American Experience talks about the epidemic from the human perspective. The 40 minute documentary on youtube talks more about the objective history of the situation.