What Cause the Violent Nika Uprising in Medieval Byzantium?

On January 10, 532, in Constantinople, a Green and a Blue supporter expected to be executed escaped and were hidden in a monastery. Three days later, the Nika revolt occurred. From the article:

"The New Reign of Emperor Justinian
Justinian had become co-emperor with his uncle, Justin, in April of 527, and he became sole emperor when Justin died four months later. Justin had risen from humble beginnings; Justinian was also considered by many senators to be of low birth, and not truly worthy of their respect.

Most scholars agree that Justinian had a sincere wish to improve the empire, the capital city of Constantinople, and the lives of the people who lived there. Unfortunately, the measures he took to accomplish this proved disruptive. Justinian's ambitious plans to reconquer Roman territory, his extensive building projects, and his ongoing war with Persia all required funding, which meant more and more taxes; and his wish to end corruption in the government led him to appoint some overzealous officials whose severe measures caused resentment in several levels of society.

Things looked very bad when a riot broke out over the extreme strictures employed by one of Justinian's most unpopular officials, John of Cappadocia. The riot was put down with brutal force, many participants were jailed, and those ringleaders that were captured were sentenced to death. This engendered further unrest among the citizenry. It was in this heightened state of tension that Constantinople was suspended in the early days of January, 532.

The Botched Execution
When the ringleaders of the riot were supposed to be executed, the job was botched, and two of them escaped. One was a fan of the Blues, the other a fan of the Greens. Both were hidden away safely in a monastery. Their supporters decided to ask the emperor for leniency for these two men at the next chariot race.

The Riot Breaks Out
On January 13, 532, when the chariot races were scheduled to begin, members of both the Blues and the Greens loudly pleaded with the emperor to show mercy to the two men that Fortune had rescued from the gallows. When no response was forthcoming, both factions began to cry out, "Nika! Nika!" The chant, so often heard in the Hippodrome in support of one charioteer or another, was now directed against Justinian.

The Hippodrome erupted in violence, and soon the mob took to the streets. Their first objective was the praetorian, which was, essentially, the headquarters of Constantinople's police department and the municipal jail. The rioters released the prisoners and set the building on fire. Before long a substantial portion of the city was in flames, including the Hagia Sophia and several other great buildings."