Mandalas are used for meditation and contemplation. They are also supposed to represent the universe, which we now know is in a constant state of change. Generally, this means mandalas are non-moving images, and (traditionally) they certainly don’t flash. This is, therefore, an attempt to update the concept of the mandala for the modern age, reflecting our current understanding of the universe.
Mandalas vibrate at frequencies much greater and subtler than flashes and pulses of electromagnetic waves.
Mandalas are made of atoms, and atoms do vibrate rapidly.