I would say that the driving intellectual factor behind Romanticism was its disdain for the accepted glorification of science and conformity as seen in the Neoclassical period. For the Romantics, such an approach took away from the very essence of being, that of an emotional frame of reference. This was something that was valued by the Romantic thinkers, in part because it was devalued by their intellectual predecessors. In fact, one can use this line of logic to analyze why the Romantic thinkers advocated much of their belief system. Whereas the Neoclassical thinkers argued that there was an objective notion of truth, the Romantics stressed the subjective nature of reality. Whereas the Neoclassical thinkers stressed the urban and cosmopolitan consciousness, the Romantic thinkers argued that true meaning can be found in the rural reaches surrounded by a natural setting.
Romanticism is a reaction against the intellectual climate that preceded it. Reason rules in the neoclassical period and in the Age of Reason, and during The Enlightenment. These are times of satire, of concentrating on the big social and political and religious issues.
Romanticism concentrates on the personal, the individual, intuition, the imagination. Romanticism stresses the opposite of what came before in almost every thought it expresses. Jonathon Swift takes on the entire British government, wealthy English, and wealthy Irish, to combat poverty, while Blake writes about the mistreatment of chimney sweeps. Romanticism breaks the issues down to the personal level.
One more example: Deism is prevalent in the Age of Reason, etc. Man is seen as preeminent and any creator is indifferent. Man's future is in the hands of man. Romanticism stresses an intuitive or transcendent connection with nature. Man communes with nature and is changed by it. Romanticism is interested in that which is beyond human understanding and reason.