This article contains spoilers for the season finale of “Succession.”

About an hour after “Succession” aired its final episode on Sunday night, Justin An spent about $1,000 on new clothes.

Mr. An didn’t want to miss out on any Memorial Day sales and had just come into the money after correctly guessing that Tom Wambsgans would succeed Logan Roy as the head of the news and entertainment conglomerate Waystar Royco.

Weeks before the show’s finale, he and four of his friends each wagered $200 on who would become the company’s new chief executive.

“I just knew it wasn’t Kendall, Roman or Shiv, none of the Roy siblings,” Mr. An, a 26-year-old marketing strategist in New York, said. “And honestly, that’s all I really had to go off of. Tom seemed like the next-best person in line for the role.”

Mr. An is one of many people who placed friendly wagers ahead of the end of “Succession.” Over the show’s four seasons of schemes, betrayals and reconciliations, fans watched as the ultrawealthy, venal Roy children (Kendall, Roman, Shiv and Connor) sought the approval of their father, Logan, and tried to make a play for the top position.

Ultimately, none succeeded, as the company was sold to Lukas Matsson, a Swedish tech billionaire. But the perennial question of who would take the throne introduced a friendly, low-stakes competition to the viewing experience. (Wagering money on websites can sometimes run afoul of gambling laws, but “casual social betting among friends” is legal in most states, said I. Nelson Rose, a gambling lawyer and expert.)

Katie Way, a journalist in Brooklyn, did not watch the first three seasons of “Succession,” but she still put her name (and $20) into a bracket pool with nine other people.

“I just started going to a watch party for the new season, and everybody I know was betting,” Ms. Way, 28, said, adding that she did not remember why she wagered on Tom, but that only one other person in her group had chosen him. “I guess I’m a little contrarian.”

By the end of the episode, Ms. Way and the other contestant had each claimed their $100. When asked what she would spend her winnings on, she said, “I probably spent more money buying wine bottles for the watch parties, so I’ll probably spend it on more food for future watch parties.”

In any game, there are, of course, losers. Shruti Marathe — who organized three different rounds of betting that included more than 60 participants across five different social groups — had her sights set on Kendall. (Money was not involved because of the elaborate betting process.)

“Even when I was watching the finale, I did not fully believe it was going to be Tom,” Ms. Marathe, a 25-year-old development manager in Los Angeles, said. A majority of those who participated in her betting series believed that Kendall would be the new face of Waystar Royco, she said.

Still, she continued, “I was satisfied with the ending, and I think Jesse Armstrong landed the plane correctly.”

After the series finale, attentive netizens pointed out that there were hints all along that Tom would take control of the company.

Some noted that Tom beat out three other competitors and shared a similar last name to Bill Wambsganss, a Cleveland second baseman who turned the only unassisted triple play in World Series history. Others said that the show’s creators had foreshadowed Shiv’s betrayal of Kendall in the finale with the Season 4 poster, where Shiv can be seen standing behind her husband, Tom, in a reflection.

Those details, though, were lost on many viewers like Riva Dhamala, a user-experience designer and Mr. An’s wife, who placed her money on Shiv. “I thought Shiv would pull a girl-boss move and steal the company out from under her brothers,” Ms. Dhamala, 27, said. “But Justin always wins,” she said, referring to her husband.

“Though, if you really think about it,” she added, “we both kind of won. I actually wear Justin’s clothes all of the time.”