Two HBO comedies, each about a group of four core friends trying to succeed in life and love; one centres on men in Los Angeles, the other features women in New York City. They both have devoted fan bases and nearly 100 episodes, racking up similar accolades and awards along the way.

Yet, when it came to movie versions (both even released in the same time frame at the beginning of summer movie season), the two series took very different paths: The Entourage movie, which opened on Wednesday, is largely considered a flop: It took in a little more than $18 million over five days, opening at No. 4 at the box office. Meanwhile, back in May 2008, Sex and the City made an impressive $57-million haul in its opening weekend, easily becoming No. 1. The movie went on to become a giant success, raking in $415 million worldwide, and spawned a much-derided sequel that made $228 million overall.

Why did seemingly parallel journeys diverge at the critical moment of making a film adaptation? It’s highly unlikely that reviews were a factor: Although most critics hated the Entourage adaptation, they weren’t exactly thrilled by the Sex and the City one either. So we offer three potential reasons for the lopsided results:

1) Sex and the City always had more viewers.

This is probably the most obvious: While Entourage debuted to about two million people, Sex and the City was already averaging around six million viewers a week. That pattern held true throughout the whole series: Approximately 10 million fans tuned in to catch Carrie Bradshaw say goodbye in February 2004. But when Vincent Chase and the gang bid farewell in September 2011, only three million people watched (and that included a repeat later the same night).

2) Sex and the City quit while it was ahead.

When Sex and the City ended, fans still craved to know more about the characters, as the finale wrapped up long-running storylines that built steadily over the years. Even though there were conclusions, there were also cliffhangers: Carrie finally ended up with Mr. Big, Charlotte got a baby, etc. Given that they had an investment in these storylines, viewers were understandably curious about what happened next.

As for Entourage, the show was sliding for awhile and interest had waned. In the series finale, Vince was on his way to getting married to a woman he barely knew. While some fans may have been mildly curious about power-agent Ari Gold quitting Hollywood to run off to Italy with his wife, there wasn’t an urgent need for the stories to continue.

3) Sex and the City was aimed at women.

Whenever a movie marketed at an underserved audience does well, the industry generally dubs it a “surprise” hit. But really, was it any shock that a female-targeted movie did so well when there are so few other options to choose from? Entourage, on the other hand, faced plenty of male-demo competition, from Mad Max: Fury Road to San Andreas. And because it was a movie that already appealed specifically to fans of the show, it simply got lost in the shuffle.