What leader has ever not fallen? That's not prophecy, that's an understanding of history and the way of the world.
But Baha'u'llah prophesised that the whole system of Empires and Kings that had existed for millennia was about to end and a new world order was soon to come.
“Soon,” Bahá’u’lláh’s own words proclaim it, “will the present day Order be rolled up, and a new one spread out in its stead. Verily, thy Lord speaketh the truth and is the Knower of things unseen.” “By Myself,” He solemnly asserts, “the day is approaching when We will have rolled up the world and all that is therein, and spread out a new Order in its stead. He, verily, is powerful over all things.” “The world’s equilibrium,” He explains, “hath been upset through the vibrating influence of this Most Great, this new World Order. Mankind’s ordered life hath been revolutionized through the agency of this unique, this wondrous System, the like of which mortal eyes have never witnessed.” “The signs of impending convulsions and chaos,” He warns the peoples of the world, “can now be discerned, inasmuch as the prevailing Order appeareth to be lamentably defective.”
Bahá'í Reference Library - The World Order of Bahá’u’lláh, Pages 161-163
He then went to proclaim the basis for a new world order or civilisation and reveal the necessary institutions and laws to accompany that order.
Causing political division in men who seek only to disprove isn't a miracle. It's calling a bluff; hell, I've done that before. It's nothing more than recognizing that your critics have no argument against you, but want to disagree for sake of disagreeing. So you press them for a point, and it's soon seen that they have none.
Even under the circumstances it was a bold move.
I also disagree with Baha'u'llah on testing god. Gods, more than anything, should be tested. A being that claims "I am god" - or more specifically, "I am the only god" - is, in my opinion, no true god. To state "Don't question me, or else!" only proves this all the more. Rather, test the gods. Go out into a thunderstorm, dare to defy Thor, and see for yourself what he is made of and capable of.
The command not to test God goes back to Moses.
Deuteronomy 6:16
Jesus emphasised it.
Matthew 4:7, Luke 4:12
The Bab chastised Mulla Husayn for taking the same approach on the evening of their first encounter, even though he was the first to recognise Him.
Its no surprise that Baha'u'llah mentioned it.
If you are right and the God you test does not exist you have demonstrated courage. On the other hand if you are wrong, then this approach is not without risk. Sometimes there's a fine line between courage and the behaviour of fools.