This paper discusses how the gladiatorial games were enjoyed by all classes - the plebs, the state, the upper class and politicians. It states that they were so popular because they served as entertainment to everyone.
From the Paper:
"Gladiatorial games were a popular and cherished event in ancient Rome. It was a huge social event for all classes, and presented its audience with appealing entertainment. Originally the gladiatorial games were part of funeral rites, although probably just for the rich due to the large expense. It was believed to honour the dead through a courageous fight to the death . "Gladiatorial shows were the chief public displays in Rome from the 3rd to the 4th Century A.D. "