Why does Ashura, in contrast to other events in history, gains more vitality over time?
Some events are forgotten over time, like a weak wave created by throwing a pebble in a pool of water-- there is a wave, but as the time passes, it becomes weaker every moment and fades away in a short time. But, there are events the other way around; they do not fade away over time; rather, time makes them more prominent. One example is the event of Ashura.