In "The Glories of Our Blood and State", why does the poet say that "There is no armour against Fate"?

The first stanza of the poem is about how titles, ranks, and symbols have no inherent “substantial” meaning. The poet is criticizing the prevailing idea in Renaissance England that one’s value as a person is determined by one’s position, or rank in society, and one’s title, or the symbols that one displays to project one’s wealth or supposed importance. The poet says that these ranks, titles, and symbols are “no armour against Fate,” meaning that disease, death, or general misfortune will befall everyone regardless of whether they happen to be a king, or a lord, or anybody else of high social rank. A king cannot use his crown to fend off death, nor his scepter.
The next lines after the given quotation are,

Death lays his icy hand on kings:
Sceptre and Crown
Must tumble down,
And in the dust be equal made.

In other words, whether a king or a peasant, we are all equal in death. Our bones will all turn to dust, as will any symbols of status like scepters and crowns. We will all, if buried, be food for the worms, and the worms won’t care if they feed on a king, a lord, a peasant, or a beggar.