What are the reasons and essence of the transition of the Bolsheviks to emergency measures in the countryside?

The main reason was simple. With complete illiteracy in the field of economics, it was necessary to get agricultural products and money to meet the needs of the state and the own needs of the ruling elite. A significant amount was consumed by the townspeople. Their number greatly exceeded the possibilities of the free market. The city was starving.
Collectivization and the fight against private property.
The ruling elite consisted of professional revolutionaries and did not recognize private property. The land became the property of the state. And the peasants, many in the past owners of this land, have become only users. The grain had to be handed over to the state at a reduced price. Such actions of the authorities caused discontent and the peasants were in no hurry to hand over the grain. The decree “On the spreading of grain and fodder” ordered the withdrawal of the required amount of the crop. Everything that the peasants produced was massively exported from the villages and villages by order. Labor service was introduced and the free sale of grain was prohibited.