First of all, it has to be said that while the term Kulak did exits, the way the term was used by the Soviets was way, way beyond the original meaning. "dekuakization" is just one term, and one that the Soviets used to hide what they were really doing. Its basically a propaganda term, historians usually speak of Collectivization.

In the end its quite simple, the Soviet Union was lead by the Communist party, and Communists, unsurprisingly hate Capitalism and the whole point of their movement is to abolish Capitalism. Capitalism means private ownership. If you had private ownership, or any ownership outside government control you were an evil exploiter. The Communist always believed those people were evil and therefore they didn't have rights and could be killed or arrested.

The Communists believed that you couldn't have Communism in the city and Capitalism in the country side. Between 1921 and 1928 they had to allow it to some limited degree simply because they were afraid the whole government would collapse if they didn't, but they had always hated at and spend lots of time debating how they could finally change this.

Attempts at voluntarily having people give up property and join collectives were miserable failures, so they knew that was not gone work.

Because of bad management of the economy and the market by 1928 the situation got worse for them, if they didn't want to have the Red Army making parades on bicycles instead of tanks they would have to do something. Turns out Communists for the most part are not that good at managing a market economy.

Stalin in full control by then, in 1928 made the decision that capitalism had the be eradicated now or the Soviet Union was not gone survive. The believe basically went that if you had ongoing capitalism in the countryside a new conservative land owning elite would emerge in the country side again that would eventually lead to a right wing coup. The opposition inside the party agree, but they felt doing at at that point would be catastrophic and destabilizing, meaning they didn't argue it was amoral or against communist policy. However Stalin argued, 'Are we communists or not?', 'Are we gone stand by our believes and do what is needed or just cower to the market until we are removed', only with much higher grain procurement could the Soviets build the tanks and everything else they needed to hopefully eradicate capitalism all over the world eventually. Once it was accomplished, even critics of Stalin said it was a monumental achievement for communism.

The real goal, was to take all control of all land owned by everybody that is not the Communist party. The propaganda was basically that the Kulaks were suppressing the others farmers, and those farmers would happily embrace the new Collective Farms once the Kulaks power was broken. The reality of course is that the 'Kulaks' were simply the most well respected local farmers that worked hard and often had good standing in the community, rather then some pre-WW1 noble landlord. What the Communist party did was simply break the power of all independent control on the country side.

The term 'Kulak' was basically applied to anybody not agreeing with party policy. You have 2 cows, kulak. You oppose shooting the guy with 2 cows in the head, kulak. You had 1 cow but didn't want to give that cow to the government collective farm, Kulak. You worked for the government and oppose shooting all the productive farmers, Kulak sympathizer. You don't want to accuse other people of being Kulaks, then your a Kulak.

I can go more into detail about how they did this if you want to follow on. So started a process of systematically moving all forms of existing agriculture into party controlled collective farms where they could extract a much higher amount of the surplus. This of course caused starvation and lots of other things, but that is not really what your question is about.

Sources:

• Stalin: Waiting for Hitler, 1929-1941

• The Harvest of Sorrow: Soviet Collectivization and the Terror-Famine