that it is the grave of al-Mughīrah ibn Shu‘bah. This matter is discussed at length elsewhere.
If we consider the Buyids and the descendants of ‘Ubayd, both groups were marked by extreme Shiism. Indeed, during their rule in Baghdad, they publicly displayed unprecedented Rāfidī rites on the day of ‘Āshūrā’, such as hanging sackcloth over doorways and sending women into the marketplaces to wail in mourning. This frequently led to fighting that the rulers were unable to stop. It was for this reason that al-Khiraqī, author of the compendium on jurisprudence, left Baghdad when reviling the early generations became widespread there. The Qarmatians in the East at that time went so far as to seize the Black Stone, keeping it with them for a considerable period, and to kill the pilgrims and throw them into the well of Zamzam.
Thus, if, despite all this, not even a shrine to al-Husayn appeared in Ascalon—although, had his head been there, the earlier generations of these people would have known this better than the later ones—then its failure to appear, despite ample eagerness and motivation, opportunity and power, establishes that the claim is false and fabricated.
This is like someone claiming noble descent from ‘Alī when it is known that none of his ancestors ever made such a claim, despite how eager they would have been to do so had it been true. This establishes that the claimant is lying. By the same reasoning, we know the falsehood of those who claim an explicit designation of ‘Alī as caliph, or anything else that people would have had abundant motivation and incentive to transmit, yet which was not transmitted.