What inspired poets of romantic era to write poems?

Wordsworth (et al) were also trying to escape from under the shadow of England's great poet Milton, who had dominated the poetic scene for the past half-century.  Whereas Milton wrote epics of religious and political seriousness, the Romantic poets wanted poetry for the common man: a simpler, more natural voice, shorter in length, fewer conventions, inspired by nature, and reflecting the spirit of the times.

There are many other influences as well: nature; the French and American Revolutions; conceptions of art (the sublime, beautiful, picturesque); and women's rights.  Also, prose (the novel) was giving poetry a run for its money in terms of popularity, so there was a shift in poetry toward prose-like conventions (intensely personal voice).

Since the Romantics, poetry has roughly been the same ever since!