What was the main motive of …

The main motive of the French was to exploit the natural resources and other essential goods from Vietnam.
The following points state that, the French succeeded in their mission
(i) For development of their own business profit, the French began to develop the infrastructural projects in Vietnam.
(ii) The French began by building canals and
draining lands in the Mekong delta of Vietnam to increase cultivation.
(iii) The vast system of irrigation works canals and earthworks built mainly with forced labour of the natives, increased rice production.
(iv) The area under rice cultivation went up from 2,74,000 hectares in 1873 to 1.1 million hectares in 1900 and 2.2 million in 1930.
(v) It exported two-third of its rice production and by 1931, Vietnam became the third largest exporter of rice in the world.