Why is Ceng Gong's "Singing Willow" a satire?

The full text of Ceng Gong's Liu Yong is as follows:

The willow branches have not turned yellow yet.

Dancing with the east wind

And its structure lives in the sun and the moon.

But I don't know that there is autumn frost between the ground and the ground

Is to write catkins with the help of the east wind, dancing wildly, unstoppable.

Derogate and ridicule those snobs who run amok when they are in power.