What did the poet see at a glance in "I Wandered Lonely as a Cloud"?

The poet's speaker says that he saw a great crowd of daffodils.
He has been feeling lonely and alienated, but the thousands of daffodils end his feeling of loneliness. They seem like people to him, swaying from side to side in the breeze as if they are all dancing in unison on the shores of the lake they have bloomed in front of.
Their swaying presence fills the speaker with joy as the bright daffodils seem to toss their heads gleefully in front of the sparkling lake. In a moment, his mood changes from cloudy and gloomy to bright and happy.
Later, the speaker often recalls the memory of those swaying, vibrant daffodils. When he is inside lying on his sofa, his remembrance of the flowers continues to give him joy.