Short answers, pulled from the story.
Chariot racing was the most popular public entertainment in ancient Rome, staged as part of religious festivals and attended by crowds of up to 150,000 in the Circus Maximus. By the fourth century AD, 24 races were held every day on 66 days each year. Emperors used the races, alongside free food handouts, to keep the population entertained and politically compliant.
Gaius Appuleius Diocles was a Roman charioteer who won 1,462 out of 4,257 career races and retired at age 42. His declared lifetime winnings totaled 35,863,120 sesterces. Even if his personal share was only a tenth of the total prize money, scholar Vamplew calculates his average annual income would have been 150,000 sesterces, exceeding the earnings of Rome's wealthiest senators.
Roman chariot racing was organized through four color-coded factions: Red, White, Blue, and Green. Each was a social and business organization that raised money, employed large staffs, and supported their drivers. In Byzantium, the Blues and Greens became the dominant factions, eventually acquiring political roles in confirming imperial legitimacy; from around the mid-fifth century, their approval of a new emperor became a formal requirement.
The Nika riots of 532 AD broke out in Constantinople against the backdrop of scheduled chariot races on the Ides of January. The normally rival Blue and Green factions united in protest over political corruption under Emperor Justinian I and came close to overthrowing him. The Byzantine military killed thousands in response, including many ordinary citizens, and historian Procopius attributed the disaster to the emperor's failure to govern effectively.
Women were banned from watching Olympic events if they were married, supposedly on pain of death, though no consistent record of that penalty being enforced survives. Women could win races through ownership: the Spartan Cynisca, daughter of Archidamus II, entered and won the Olympic chariot race twice as owner and trainer. Unmarried women were permitted to watch the races.
The last known chariot race at the Circus Maximus in Rome was staged in 549 AD by the Ostrogothic king Totila, though whether it was a formal race or a display of horsemanship is uncertain. In Byzantium, chariot racing continued in reduced form until the imperial court moved to Blachernae during the twelfth century, making the sport one of the longest-running continuous entertainments in the ancient world.