The crown is fallen [from] our head
Or, "the crown of our head is fallen" F1; all their honour and glory as a nation were gone; the glory of their kingdom and priesthood, to both which a crown or mitre belonged; the glory of church and state. Aben Ezra interprets it of the temple, the place of the divine Majesty. Sanctius thinks there is an allusion to the crowns they wore upon their heads at their feasts and festivals; and so the words have a close connection with what goes before: woe unto us that we have sinned!
which had brought all these evils upon them: this is not to be considered as an imprecation or denunciation of misery; but as a commiseration of their case; calling upon others to it, and particularly God himself, to have mercy upon them; for, alas for them! they had sinned, and justly deserved what was come upon them; and therefore throw themselves at the feet of mercy, and implore divine compassion.