It would be a mistake to see Virgil’s poetry as purely political propaganda.  It was a matter of self-respect for Augustus to allow artists to do their art.  He genuinely wanted to be admired for what he did for Rome – not for what he could do to you. His victory and the peace it brought were things most Romans celebrated. He restored religious rites, brought stability, and made peace with foreign enemies. These were all good things and the poets would have thought so too. There was no direct intervention in what they wrote or censorship. To have any value, the great poets needed to be left to write their own way. At one point Virgil even considered writing an epic about Augustus himself.