Wordsworth's poetry became so popular to a large extent because of the way that it represented a completely new way of looking at poetry, and in this sense was quite revolutionary. The publication of Lyrical Ballads, which Wordsworth co-authored with Coleridge, represented something of a watershed in the history of literature in the 18th century. The new movement of literature was called Romanticism, and was characterised by a focus on the importance of feelings to humans and lush, lavish descriptions of nature and how it impacted man. Consider, for example, the following quote from one of Wordsworth's most famous poems, "Tintern Abbey," in which he talks about the impact that nature's "beauteous forms," or the beauty of nature, inspires him:
Nor less, I trust,
To them I may have owed another gift,
Of aspect more sublime; that blessed mood,
In which the burthen of the mystery,
In which the heavy and the weary weight
Of all this unintelligible world,
This poem, as indeed occurs in so many of Wordsworth's poems, explores the feelings of man and in particular how nature can act as solace and balm to man's soul. Before the publication of Lyrical Ballads, poetry had reflected the overwhelming mantra of the age, which favoured reason and logic and neglected feeling. Wordsworth sought to challenge this, and through his challenge, ushered in a completely new literary movement. It is for these reasons that his poetry is so enduringly popular, as it takes as its focus man's connection with nature, and through this, explores something that is essential to all of us.
In addition to the appealing ideals of Romanticism in his poetry with the importance of the individual's imagination and the conviction that Nature offers solace and succor to the troubled soul, Wordsworth's poetry broke from stilted language and was written in blank verse, allowing for easy comprehension because it approximates natural spoken English. Yet, such verse still evokes "immense grandeur" because there is a musicality to it.
Indeed, Wordsworth's poetry gained popularity because the subject matter is not extraordinary and is thus comprehensible to all, while at the same time it appeals to the imagination and senses immensely with its imagery and musicality. Consider the opening lines of Wordsworth's autobiographical The Prelude:
OH there is blessing in this gentle breeze,
A visitant that while it fans my cheek
Doth seem half-conscious of the joy it brings
From the green fields, and from yon azure sky.
Truly, there is something in the poetry of Wordsworth that awakens the memory, communicating with the heart and soul of the readers/listeners that transcends them from the unremarkable and banal of quotidian life.