Why were there two different views about the way in which korea might be reunified?

Communism v. Capitalism/Democracy--the UN split Korea along the 38th parallel and the North was under USSR influence and the South was under Western influence from the US. 

The North and the USSR believed Korea would be best to be unified under a communist government and the South and the US believed it would be best to unify Korea under a democratic government. The Korean War began with the North making an attempt to unify the country.