Why might people have identified Richard Cory as the embodiment of success?

The townspeople in Robinson's "Richard Cory" look at Richard Cory as an example of success based on his appearance and mood while walking around the town. This is why the ending of the poem—when Cory commits suicide—is such an ironic and surprising twist.

The first stanza reads:

Whenever Richard Cory went down town,

We people on the pavement looked at him:

He was a gentleman from sole to crown,

Clean favored, and imperially slim. (1-4)

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The townspeople in Robinson's "Richard Cory" look at Richard Cory as an example of success based on his appearance and mood while walking around the town. This is why the ending of the poem—when Cory commits suicide—is such an ironic and surprising twist.

The first stanza reads:

Whenever Richard Cory went down town,

We people on the pavement looked at him:

He was a gentleman from sole to crown,

Clean favored, and imperially slim. (1-4)

Cory is described as a "gentleman," which could indicate both good manners and high social class. The word "imperially" links to the latter meaning, as it is related to emperors. He seems powerful and attractive. 

The next stanza continues:

And he was always quietly arrayed,

And he was always human when he talked;

But still he fluttered pulses when he said,

"Good-morning," and he glittered when he walked. (5-8)

Even though Cory is described here as "always human," so not that different from the townsfolk, "he fluttered pulses" and "glittered." He is placed on a pedestal by the town, and every action is considered special.

The third stanza makes Cory's wealth obvious:

And he was rich—yes, richer than a king—

And admirably schooled in every grace:

In fine, we thought that he was everything

To make us wish that we were in his place. (9-12)

Here, he is said to be "richer than a king," and due to his wealth and "grace," the townspeople want to be "in his place." This becomes ironic in the final stanza because, as they struggle, he "Went home and put a bullet through his head" (16). This is surprising because the townsfolk think his wealth, manners, and gentlemanly nature make his life perfect. They envy him and wish to trade places with him. Obviously, there was something about his life, though, that was not perfect. His own perception of himself does not match the perception of the town.