Even before the election of the Workers Party to government in the North, th Soviet administration had permittee a number of reforms (by the short-lived Korean Peoples Republic). Any Korean who had collaborated with the Japanese was thrown out of office. In March 1946, a \land reform program had been implemented. The large tracts of land owned by the traditional Korean aristocracy (about 5000 landlords) and any land acquired by Japanese individuals or companies was confiscated ( individuals were allowed to keep approximately 12 acres) and redistributed to peasant families.Most landowners had already fled to the American occupied south, so the land re-distribution was accomplished without much violence. Major industries were confiscated by the state. Labour reforms (an 8 hour day, social security insurance, pay increases, equal pay for men and women) were also implemented. Generally, Korea, Old and New: A History notes that the reforms were carried out by Koreans and reflected the spirit of the Korean People's Republic.
A Soviet-US Joint Commission (established to work toward a single provisional Korean government first met in 1946 and also in 1947 but it was soon clear that little progress was going to be made, because of the differing views of the north and south. In the north Kim Il-sung had emerged as a potential leader and it seems he set about establishing control of both the Workers Party and a Soviet backed 'Interim People's Committee' set-up in February 1946. Later in 1946 a military corp was initiated that would eventually become the DPRK's Army.
In the south, the American Military Government brought Syngman Rhee (who had spent many years in the USA) to Korea. Rhee had a reputation as a patriot (and you may recall had been tapped as the head of the Korean People's Republic and was also a fervent anti-communist and was soon denouncing anyone who wanted to work with the Korean People's Republic, and any Korean communist group (in the south or the north).
The American Military Government made an effort to establish a moderate 'centrist' political group, but in the fast polarising political situation, there was little support.
Given all those developments it soon became impossible for any UN sponsored move to establish an independent Korean government.
The North reflected the leftist spirit of many Koreans, who had long dreamed and fought for a socialist state, while in the South an alliance between those opposed to such a move, wealthy business men, southern landowners, northern landowners who had lost their landed estates, and former collaborators with the Japanese Colonial Administration was soon seeking control of the south's political aspirations.
Both groups claimed to represent all Koreans. Both groups were soon talking about using force to achieve a 'unified' Korea, a situation developed is precisely what we still see on the Korean Peninsula.
In May 1948, elections were held in the south, the new National Assembly adopted a constitution and on August 15 of that year, the 'Republic of Korea' ( i.e. South Korea) was proclaimed, Syngman Rhee became President.
The north's reaction was to hold their own elections on August 25, and proclaimed the 'Democratic People's Republic of Korea' with Kim Il Sung as premier in September. Both of these governments adopted an attitude that there were the only legitimate government of Korea.
A little later in 1948 the USSR occupation army withdrew from north Korea, and in June 1949 the USA withdrew their military forces. Both states began to talk of a forced reunification with increasingly violent rhetoric, (somewhat like the Kim Jong-u - Donal Trump exchanges of late).
What can we say now after all these events, was the fate of that one opportunity for a unified Korea that existed in 1945 - the Korean People's Republic? Its fair to say that in the north, it was subverted by the USSR and the combined Korean Communist Party/Korean Worker's Party and Kim Song I.
In the south, it was ignored by the American Military government and atrophied away.
But just how did the war that started in 1945 develop?