For Marcus (Aurelius) lived a grand contradiction: an emperor reduced by wisdom to one skeptical of duty and purpose, to its inner vitality and beneficence. He was reduced to fideism (echoed centuries later by another fideist, Montaigne), wherein duty is followed not because it is good but because ethics consists in the necessity to carry out our duty, as if the carrying out alone was ethics, even when the duty is not intrinsically good and could no longer engender faith. Indeed, duty in this sense was Rome itself for Marcus, necessary to defend and maintain even when he no longer believed in its efficacy.

Duty and purpose are dubious worldly enterprises. Yet Stoicism is the philosophy resonating with the perception of failure, attracting intelligent Romans caught within their own unraveling, both of their person and their world.

This reminds me of something from John Ralston Saul:

But it is virtually impossible to maintain healthy scepticism when power is in your hands. To do so would require living in a state of constant personal conflict between belief in your public responsibilities and self-doubt over your ability to discharge them.

And something else from Nietzsche:

Dionysian man shares this affect with Hamlet: both have seen into the very essence of things, they have understood, and are repelled by, the thought of action, since no action of theirs can change anything of the eternal essence of things, and they consider it absurd, or even shameful, to be expected to be able to generate order in a world of chaos. Understanding destroys action, and action depends on a veil of illusion.