I see the delay is in our exceptance of the Mahdi, the Prohecy is unfolding as we did not heed the call to peace and unity.This is what I keep saying, that Quran is full of conditional prophecies. They are promises but with conditions. One of these promises if you keep in mind all the talk about past cities destroyed, is that the universal Messenger (ie. the Mahdi) will be a trial for all cities, and whoever denies him, will be physically destroyed. I say physically since the mini context within the Surah as well the broader themes of destroyed nations and cities all point to this meaning. But it's also a prophecy meant to be avoided and warnings is to make us avoid this. The delay of Imam Mahdi (a) appearing has to do with making the world avoid this dark prophecy that will come about if they don't heed the warnings.
Remember, those that denied persecuted and banished Baha'u'llah were the Islamic Nations.
I would just offer the events of our time and the suffering we are now witnessing across Islamic Nations, which inturn, is reverberating around all Nations.
The destruction has just begun, I offer a thought under the spoiler.
Once Varqa asked Baha'u'llah, "How will the Cause of God be universally adopted by mankind?" Baha'u'llah said that first, the nations of the world would arm themselves with infernal engines of war, and when fully armed would attack each other like bloodthirsty beasts. As a result, there would be enormous bloodshed throughout the world. Then the wise men from all nations would gather together to investigate the cause of such bloodshed. They would come to the conclusion that prejudices were the cause, a major form being religous prejudice. They would therefore try to eliminate religion so as to eliminate prejudice. Later they would realize that man cannot live without religion. Then they would study the teachings of all religions to see which of the religions conformed to the prevailing conditions of the time. It is then that the Cause of God would become universal.
Regards Tony