What is the significance of the word ‘for’in the beginning of the last stanza?

Sometimes, the word ‘for’ like conveys the sense of ‘because.’ Here too, the word ‘for’has been used to indicate that this stanza is going to provide us with the explanation why the poet says that watching the ‘show of flowers’ gave him ‘wealth.’ He makes it clear why the sight of the flowers was so significant in his life. Whenever he lies on his bed in a vacant or reflective mood, the daffodils flash on his inner-eye, that is, his imagination. The daffodils have become the eternal remembrance of the poet, whenever he is lonely. So, he calls it the ‘bliss of solitude,’ the blessing of being alone.