Voldemort's Followers
The evil villain Voldemort was vanquished in “Harry Potter and the Deathly Hallows.” His followers dispersed. Evil is vanquishted. Story over. The book jumps 19 years ahead. It leaves you wondering what happened in those 19 middle years? The first time Voldemort was vanquished, there were trials and former Death Eaters disavowed Voldemort or faced prison. One could surmise that happened again. After the first time, Lucius Malfoy tried to assist Voldemort’s return with his diary. He kept connections in government and used those connections to undermine Voldemort’s enemies. What happened to the Lucius Malfoy’s of the world the second time. They had no one to reinstate. They had no one to follow. Who filled the power vacuum? It wasn’t Draco.
On the other side, the Ministry of Magic was weakened. Hogwarts was a mess. There were power vacuums in both.
Was it 19 years of power grabs and confusion? “Cursed Child” answers some of those. There is room for more exploration.