In this modern era, World War 3 would be its biggest catastrophe, now that technology is this advanced, weapons have also become advanced enough to wipe a nation out of existence, to the point that technology becomes the focal point of the war should it ever arise.
This had already become history. World War 3 indeed became the biggest catastrophe, humanity's greatest struggle, and the world's final stage, because if another were to happen, no matter how long the wait, the world will end right then and there.
So a man made it so that this will never happen again, he figured out humanity's greatest curse, which is technology, something he contributed very heavily his entire life, the moment he realized his inventions became more than just innovation, he pulled the kill switch of his inventions which are almost all the technology of the world, and left humanity with it, leaving humanity with no technology, returning them to the stone age.
This was the moment where humanity looked for more than just technology, and despite recovering some of their technology, they accidentally discovered magic along with it.
Of course, this has adverse effects. People began a revolution of magic to attempt to overthrow the leaders, unnatural phenomena appearing like monsters that vary from goblins to dragons, even aliens entering their world for the first time, and so much more.
The world is in disarray again, no one and nothing makes sense anymore, so what it needs the most are new leaders, people who can lead this new era of technology and magic, teach people magic, and those who can defend and fight for humanity's standing in this new reality, a reality of magic.
They are called The Kings.