How did John Milton impact the Renaissance era?

Milton's impact on English literature overall did not really occur until after his death. By this time the period we label "the Renaissance," even in its broadest sense, was over. When Paradise Lost was published in the late 1660's, the Restoration of the Stuart monarchy had occurred and Milton, because of his unchanged political views and his having served in the Commonwealth under Cromwell, was now persona non grata with the regime. Apart from the personal isolation (and even his brief time in jail) this entailed for Milton, Paradise Lost was stylistically out of touch with current trends. Milton wrote in blank verse when the new trend was to employ rhymed couplets. The severe religious message of his epic was also out of step with the more carefree, anything-goes literary and social atmosphere of the Restoration.
Soon after his death, however, Milton came to be recognized by many as the greatest of all English poets. Despite political, religious and aesthetic differences, John Dryden and Alexander Pope considered Milton an epic poet equalling or even surpassing Homer and Virgil. Decades later, in his Lives of the English Poets (1779), Samuel Johnson expressed similar views. Despite the changed aesthetic of the nineteenth century, the Romantic and Victorian writers extolled and idolized Milton, seeing in him not only a great poet but a courageous individual who remained firm in his beliefs while others conveniently switched their political allegiances in accordance with the regime changes of the time.

Renaissance literature is known for the elevation of the sonnet form and the drama. John Milton, a poet and scholar, influenced the period by ushering in the return to the epic, a longer poetic form. Milton wrote in a variety of poetic forms, including the sonnet, but is best known for the epic Paradise Lost.
As a Puritan and supporter of Cromwell in the English Civil War, Milton approached the story of Lucifer's fall from Heaven and the subsequent temptation he poses to Adam and Eve as an allegory. On one level it retells the story of Genesis with purely religious implications. On another level, he uses that very story to describe the English Civil War, with the omnipotent God representing the king, and the inspirational Lucifer, who demands equality with God, representing Cromwell.
The political and religious implications of the work influenced the culture and society of the time. Additionally, the actual poetic form encouraged a transition to longer works by Alexander Pope and others who transitioned from the Renaissance to the Enlightenment.