Complex sentence: If vacant, subliterary spectacles were not enough of a threat to dramatists, opera, which had crossed over to England in the Restoration, experienced an enormous surge in popularity with Italian grand opera in England in the 1710s and 1720s.
Split into simpler sentences: If vacant, subliterary spectacles were not enough of a threat to dramatists. Opera, which had crossed over to England in the Restoration, experienced an enormous surge in popularity with Italian grand opera in England in the 1710s and 1720s.