South Vietnam
The unpopularity of the US army among the Vietnamese population was heightened as a result of its association with the Diem government.
The majority of the population supported the Vietcong. The Vietcong seemed to offer improved social and economic structures that would come with a communist victory.
Corruption
Diem refused to carry out land reform. Instead, he gave the land to his supporters and friends. These landowners extorted the peasants who worked on their land.
Oppression of the Buddhist faith
The majority of the people were Buddhists, but Diem and his government of Catholic landowners persecuted them. Among other things, they were not allowed to celebrate Buddhist holidays or fly the Buddhist flag on Buddha’s birthday.
This led to many protests including letters written in the blood of monks and self-immolations (people setting themselves on fire). The self-immolation of Quang Duc in 1963 led to many copycat burnings.
Freedom of Speech suppressed
The National Liberation Front (NLF), which consisted of South Vietnamese people, was set up in 1960 to oppose the Diem government. However, supporters of the Vietcong were hunted down and put in prison camps.