Reasons for the fall of Okello's regime.

The head of State himself was a man with very low education that he could not control political events in the country. Surprising he could not even make a full state address in English. Amin was far better than him in terms of knowledge and personal charisma
Lack of adequate preparation. The two Okellos, Tito and Basilio took over power without knowing who was to become head of state and they lacked a well-laid programme for their regime.
Bad behaviour of the army. The UNLA under the new regime went on rampage without much control. They terrorized Kampala by raping women, looting property from shops and torturing civilians for no reason.
 
Lack of support from the civilian population. This was because of their bad record even in Obote’s government and therefore people in Kampala refused to support the regime.
The confusion in the regime. The members of the junta did not know what to do with the power they had got. Power sharing became a problem until they started killing some of the new members who had just joined them.
Failure to identify acceptable politicians. From the beginning the Okellos were just looking for acceptable people to rule Uganda. Paul Muwanga was rejected by people as Prime Minister, likewise Waligo was not popular.
Appointment of the cabinet did not know well. There were Ministers who were not ready to serve the regime but they accepted because they wanted their names to be recorded down in the books of history that they once were ministers on earth.  Other people like Sam Kutesa, Kawanga Ssemogerere, Timothy Wangusa were committed elsewhere.
Failure to co-operate with the politicians and the fighting groups.
The opposition by the NRA guerilla fighters undermined the regime because it was not possible to fight the rebels at that time.
The reaction of other fighting groups much as they joined the regime, they remained indisciplined that they created disagreements in the regime.
The involvement of former Amin’s soldiers with their bad record of killing about half a million Ugandans
Failure to implement decisions of the Nairobi peace talks.
Lack of recognition from foreign governments.
Failure to implement rule of law apart from anarchy.

National Movements and New States in Africa