The Demon King must have plotted all of this.
The energy around the whole world right now is chaotic and that is actually an understatement. Some of the Laws of the world went crazy and wild, creating weird phenomenon that affects Heaven and Earth
It would take time for it to reached an equilibrium.
This is the perfect moment for the Demon King to do something unnoticed.
The Demon King death created a blast of energy that shakes the whole world.
This energy was so potent, so powerful that it disrupts the Laws and the energies all around it.
On many parts of the world this instability in the energies of the world and the disruption of the very basic laws that keep the whole world going had created a lot of chaotic energies storms that ravages the whole world
One of the side effect of this disruption of energy is that it makes anyone unable to easily use any energy related abilities