While there are many differences between the ancient and modern Olympics, both have been subject to criticism of all time. And some historians point out that the ancient iteration of the games was corrupt in its own way.
According to many Greek historians, the ancient Olympics belonged to a "golden age" of sorts of Grecian history. From the years of 500-440 B.C., the games were pure in the sense that the athletes competing were focused on the honor that came from participating, rather than financial gratification. However, it didn't take long for the money side of things to sneak in. And for many, it brought about the demise of the competitions' integrity. As the sports rose in popularity, the notion of "professional sports" came to prominence. And from there, athletes became more interested and invested in prizes and the whole ordeal became nothing but a cash grab.
Norman Gardiner, a British historian, broke the timeline into two distinct periods to aid in understanding. According to him, there was the "pure" era of the sport where noblemen competed for the honor. Then, came the "corrupt" period dominated by lower-class Grecians competing for financial gain. However, there were some historians that challenged the view, and instead noted the prize element which has existed in the games from the get-go. The Panhellenic Games awarded winners garlands constructed of sacred greenery including olives, celery, and pine. In addition, there was evidence of olive oil being awarded to some competitors.
So, just like the modern Olympics, it seemed as though there were some fans and some critics in the crowd. But one thing was for sure, it made a lasting impact on the centuries to come.