He was not unintelligible because he was proud, but unintelligible because he was humble.

He was not unintelligible because his thoughts were vague, but because to him they were obvious.
A man who is intellectually vain does not make himself incomprehensible, because he is so enormously impressed with the difference between his readers' intelligence and his own that he talks down to them with elaborate repetition and lucidity.

What poet was ever vainer than Byron?
What poet was ever so magnificently lucid?
But a young man of genius who has a genuine humility in his heart does not elaborately explain his discoveries, because he does not think that they are discoveries.

He thinks that the whole street is humming with his ideas, and that the postman and the tailor are poets like himself.

Browning's impenetrable poetry was the natural expression of this beautiful optimism.