There is no "contradiction" in The Waste Land in this regard.
The Fire Sermon underscores the maladie in Buddhistic and Christian terms both of which concur in their diagnosis of the wasteland situation..
The fourth section of TWL opens with the title "The Fire Sermon" which is an allusion to Buddha's Fire Sermon.
Eliot's Notes: 308. The complete text of the Buddha's Fire Sermon (which corresponds in importance to the Sermon on the Mount) from which these words are taken, will be found translated in the late Henry Clarke Warren's Buddhism in Translation (Harvard Oriental Series). Mr. Warren was one of the great pioneers of Buddhist studies in the Occident.
In the sermon, the Buddha instructs his priests that all things "are on fire. . . The eye. . . is on fire; forms are on fire; eye-consciousness is on fire; impressions received by the eye are on fire; and whatever sensation, pleasant, unpleasant, or indifferent, originates in dependence on impressions received by the eye, that also is on fire. And with what are these on fire? With the fire of passion, say I, with the fire of hatred, with the fire of infatuation."
This section of the poem closes with St Augustine, a proponent of Christianity:
To Carthage then I came
Burning burning burning burning
Lord Thou pluckest me out
Lord Thou pluckest
Eliot's Notes: 307. St. Augustine's Confessions: 'to Carthage then I came, where a cauldron of unholy loves sang all about mine ears'.
And this is crucial:
Eliot's Notes: 309. The collocation of these two representatives of eastern and western asceticism, as the culmination of this part of the poem, is not an accident.
Part V of TWL, then, offers the solution in Christian and Upanishadic terms -- both reinforcing each other.
In Part V, there is the journey to Emmaus, as well as the approach to the Chapel Perilous.
The arrival at the Chapel Perilous is followed by a change of scene and there is rain:
There is the empty chapel, only the wind's home.
It has no windows, and the door swings,
Dry bones can harm no one.
Only a cock stood on the rooftree
Co co rico co co rico
In a flash of lightning. Then a damp gust
The situation finds a parallel from the East:
Ganga was sunken, and the limp leaves
Waited for rain, while the black clouds
Gathered far distant, over Himavant.
The jungle crouched, humped in silence.
Then spoke the thunder
Eliot's Notes: 401. 'Datta, dayadhvam, damyata' (Give, sympathize, control). The fable of the meaning of the Thunder is found in the Brihadaranyaka--Upanishad, 5, 1.
The Waste Land concludes by underscoring the resolution in Christian and Upanishadic terms:
Poi s'ascose nel foco che gli affina.
[Purgatorio, xxvi :
'Ara vos prec per aquella valor
'que vos guida al som de l'escalina,
'sovegna vos a temps de ma dolor.'
Poi s'ascose nel foco che gli affina.]
Datta Dayadhvam Damyata