Why did Sylvia Plath write the poem of "Lady Lazarus"?

Why does anyone write anything?  To speculate is to
diminish the art.  The New Critics would not like this
question...

Poetry is confession, catharsis, therapy, a way
of making sense of the world, a chance to have one's words immortalized, and
puzzle-making: putting the perfect words in the perfect order.  Namely, the poem is her
most mature attempt to make sense of her mental illness (which lead to previous
unsuccessful suicide attempts), her family (father and mother), her ex-husband, and the
cruelty, dehumanization, and absurdity of the modern
world.

Plath attempts to be absurdist and confessional poet
in "Lady Lazarus," her magnum opus along with "Daddy."  Anne Stevenson lauds the
paradoxical complexity of Plath's poetry, saying it "is all of a
piece":

Its
moments of tenderness work upon the heart as surely as its moments of terror and harsh
resentment. And despite her exaggerated tone and the extreme violence of some of her
energy, Plath did, courageously, open a door to
reality.

Stevenson goes on to
praise Plath's "Lady Lazarus" persona "with its agressive assertion of regeneration,
rejoice[ing] in so much verbal energy that the justice or injustice of the poet's
accusations cease to matter."

The poem does not condone
suicide.  Rather, it rises above it, if only for a moment.  Her poetry works best in
barrage: imagery against men, materialism, sexism, self, suffering, and tradition.
 Regardless of the poet, the poem, like all good art, affirms and breathes
life.