Why does Eliot use St. Augustine and Buddha concurrently in The Waste Land?

This is a fairly powerful question on a very intense work
sample.  I am not sure any one person can claim to have "the answer" for any question in
a work like Eliot's, so be warned on this front.  In my mind, Eliot's use of religious
figures from different venues as Christianity and Buddhism is a reflection of the
Modernist style in the work.  Eliot is seeking to broaden understanding in making the
argument that the traditional methods of establishing meaning have failed.  Christianity
is a part of this, and its failure is something that drives Eliot in the work.  The
rigid function and dogmatic laws of Christianity cannot offset the decline and crisis
that exists in the modern setting for thinkers like Eliot.  The inclusion of Buddha
might be a call to demand new ways of thought in such a moral and psychological abyss
that looms over the lives of the people in the poem.  Additionally, Eliot might be
suggesting that Augustinian edicts cannot prevent the sense of disillusion in the modern
setting and to invoke someone from a diametrically opposite religious point of view as
Buddhism might be a way to highlight this.  If one didn't like this read, perhaps
another, and more drastic, one could suggest that both thinkers seek to overcome the
world of the mortal, but cannot.  The section in which Eliot uses both figures is one
where individuals are pitted between the crushing nihilism of the modern setting set
against the desire to be free from it.  The act of sex, which is present in the section,
is in its own right an act that is both of this world, and one that strives to be free
of it.  The physical ecstasy of sex, or its perception, drives one into its clutches,
but each of the characters in the poem are cursed in that the more mundane and banal
aspect of sexual activity reflect a fundamental sense of waste and lack of
transcendence.  To this end, both religious thinkers might be exactly representing this,
and to bring them both together could be a way for Eliot to suggest that no matter the
thought or the philosophical leaning, crisis and disillusion follow all
individuals.