How does Willy's position as a salesman have thematic significance in Death of a Salesman?

There is great thematic significance in Willy's job. The
play illustrates the bewitching yet destructive force of the American Dream, and Willy's
identity issues and lack of success are enmeshed in the dream and the demands on a
salesman.

Willy is not a 'natural' salesman, he is 'foolish
to look at, old, exhausted and delusional. Willy is driven by the image of Dave
Singleman, a supremely successful and popular salesman, whose demise gives us the title
of the play. It is as if Willy's whole life has been directed to him achieving
popularity - he is so desparate for recognition but can see it happening only after his
death.

We learn through Willy's flashbacks that he has
never been successful. He missed out on the opportunity to make his fortune like his
brother, Ben, and still calls upon his long-absent brother for advice. He cannot see
that the wealth he has is his family. He does not even hear when Ben tells him
this-

    BEN:William, you're being first-rate with your
boys.

We are never told what Willy is supposed to sell, and
this is an irrelevant detail. What Willy was supposed to sell was himself, but this was
never Willy's strength. As Biff says in the Requiem-

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BIFF: He had the wrong dreams, all
wrong.

Willy was good with
his hands: he had done lots of work on his house. He was more suited to creating and
making rather than selling. Charley tries to explain the purpose of a salesman, and it
is here we realise just how mismatched Willy and his career
were-

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CHARLEY:...He don't put a bolt to a nut, he don't
tell you the law or give you medicine. He's a man way out there in the blue, riding on a
smile and a shoeshine. And when they start not smiling back-that's an
earthquake.

Willy had faced
the earthquake much earlier in his career but, trapped by consumerism, debt and
ambition, Willy is condemned to follow his path to his death.