Why was Pol Pot so fixated on the idea of a country full of farmers ? The more I think of his plan for Cambodia the more confused I become. What was his plan for producing vehicles and farming supply’s and what would he do if people under his regime got sick since he killed most doctors.
I feel like there is a bit of a misconception here about what the Communist Party of Kampuchea wanted to do. You get phrases like 'year zero' thrown around - which is not something that the regime ever said - and people get the idea that the Khmer Rouge just wanted to take Cambodia back to the stone age and stay there. As you mentioned, they did have ideas about developing into a modern, industrialised communist state. It is just that they were not very precise in how they thought they would attain this, and their plans failed relatively quickly - as did their entire project.
The emptying of the cities, the equalisation of the population, the idealisation of the peasant, these were all part of a revolution which aimed to become a communist society in record time. They called it the 'super great leap forward', with a rather obvious nod to their Maoist benefactors. The CPK wanted a pure revolution, they wanted to transform as much of the country as possible into one big collective farm, this was in order to produce enough surplus rice that they would be able to fund light industry, then heavy industry.
The idea was that a sufficient 'revolutionary consciousness' would be able to drive this revolution forward, just like the great leap forward, but Pol Pot et al were unaware at how spectacularly that project had also failed in China. Initially all of their transportation and many kinds of machinery etc was all sourced from China, so they still had access to technology but Cambodia hadn't had much of something resembling an industry production sector prior to the revolution anyway.
It can be confusing if you look at what they did and what they were aiming to do, the two projects don't seem to make any sense. But in their minds, they believed in an innate Khmer ingenuity and tried to focus that into 'self mastery', if they could purify their new country into a population that was full of pure revolutionaries they thought that anything was possible. When it started to fall apart, they blamed the population, they blamed themselves, they blamed outside influence like the Vietnamese. Eventually the regime imploded and in the meantime their communist utopian project had killed more than two million people.