Brief background: I have been an options trader for 7 years and I was a successful online poker player in the mid 2000s. Damn I'm getting old.
In general, most answers to this question are good answers like the one Andrei Kolodovski gave in this thread. Certainly there are similarities between poker and trading. Here are the key ones in my opinion:
– You make lots of bets with incomplete information. There is a big difference between trading/poker and a game like chess, where you know where all the pieces are.
– You must understand and embrace variance. In my experience, the best poker players and the best traders are able to perform at a high level whether they are making money or losing money. For me, this is the one major skill my poker education gave me.
– You have to have an obsession with edge. It is very important for both poker players and traders to understand where their profitability comes from. Often markets/people change and you have to adapt and improve to remain profitable.
But here's the truth: finance professionals are almost always terrible at poker. And it's the best kind of terrible to play against because many traders/investors think their skills will translate into poker, and have no idea they are terrible at poker.
Here's the bottom line: poker is hard. When I was competing at a high level in poker, I played 40+ hours of poker a week. Then I spent another 10-15 hours analyzing my hands by using software and by discussing individual hands with other top players. I did this for almost 4 years of my life. One year after I took a full-time job in finance, I probably went from being one of the best 200 players in the world to the 20,000th best player.
Another thing about poker is that it is much harder to get good at poker now than it was before Black Friday. It is much easier to get better at poker if you can play online. In person, you might play 20-30 hands an hour if you are lucky. Online, you can comfortably play 4+ tables at 60 hands/hour. You can also easily import your hands into a database and fix problems with your game. You can actually play a meaningful sample size of hands and draw real conclusions from your results. Many finance professionals who play poker have never played online. The ones who are good have usually played a bunch online. It requires a ton of time playing live poker to get very good.
What makes poker the best game in the world is accessibility and short-term luck. Anyone can beat anyone on a given night (unlike Chess where I will lose to Magnus Carlsen every time with no exceptions). Anyone can win a poker tournament. This is why poker is so popular.
Because of the luck involved, it is almost impossible to deduce poker skill based on in-person results. The financial press loves to make a big deal when a finance guy makes a deep run in a poker tournament… but luck is by far the biggest factor to winning a single poker tournament, not skill.
To sum it all up, poker is hard. The vast majority of big-shot finance guys who are listed as great poker players are mediocre at best. Most of these people are way too busy running a business and/or trading to be able to invest the time required to get good at poker. There is certainly some overlapping skills that successful poker players and traders have–but that doesn't mean every good trader can play poker!