To enrich the British (and specifically the British) and the local elites they were aligned with at their opponents' expense. As importantly, it doesn't seem to have had any clear effect on development itself - it would depend a lot on those local elites if there would be any positive effects for their societies at large. A classic case of how the quality of elites (who are the ones who have the greater means to shape institutions and concrete policies) matters for the collective good.
(This is a version of the 'White Man's Burden' argument.)
As a poet of imperialism, Kipling urges the American reader and listener to take up the enterprise of empire, yet warns about the personal costs faced, endured, and paid in building an empire; nonetheless, American imperialists understood the phrase The white man's burden to justify imperial conquest as a mission-of-civilisation that is ideologically related to the continental-expansion philosophy of Manifest Destiny of the early 19th century.
The title, the subject, and the themes of "The White Man's Burden" provoke accusations of advocacy of the Eurocentric racism inherent to the idea that, by way of industrialisation, the Western world delivers civilisation to the non-white peoples of the world.