a contrast between a person with a certain reported greatness and the simple person whom they loved, who does not rise to or appreciate his greatness.
The poem could be taken as calling human greatness into question as a whole, or as carefully proposing an alternative view of real human greatness.
...
A shilling life will give you all the facts:
How Father beat him, how he ran away,
What were the struggles of his youth, what acts
Made him the greatest figure of his day;
Of how he fought, fished, hunted, worked all night,
Though giddy, climbed new mountains; named a sea:
Some of the last researchers even write
Love made him weep his pints like you and me.
With all his honours on, he sighed for one
Who, say astonished critics, lived at home;
Did little jobs about the house with skill
And nothing else; could whistle; would sit still
Or potter round the garden; answered some
Of his long marvellous letters but kept none.