There are three statements in this verse: (1) the creation was subjected to vanity; (2) this subjection was not voluntary, but imposed by God; and (3) the very subjection is a basis of hope, for otherwise there would have been no point at all in granting to rebellious humanity any further tolerance at all.
All of the vain things that so charm, seduce and dominate the lives of people during their brief pilgrimage upon earth are actually endowed with no more permanence than a mirage. Whatever glory or eminence may come to man is only for the fraction of a moment; he builds for himself a house, a palace or an empire; but the whirling suns brush him into the grave, and where is he? Whatever achievement, success or honor may place upon his head for an instant some distinction or accolade, tomorrow cannot remember it. This tragic quality of all human glory is the reason why the apostles taught Christians to look to the unseen, the invisible realities of hope and faith in Christ for their true fulfillment. BCC -> Commentary on 2:17 -open-