The argument is flawed because the premises don’t tell you that those are the only qualities of successful financial advisors. By way of analogy, consider:
“Most good surgeons have steady hands and are calm under pressure. Since Bob is calm under pressure and has steady hands, there is a good chance he could be a good surgeon.”
In terms of content, maybe the most obvious problem is that we don’t know if Sean is smart enough to get through medical school. Or good enough at science classes. The premises are to be accepted as true, but the argument is flawed because the premises don’t (in my example or the one you entered) give you enough information to reliably reach the conclusion. There may be other characteristics – necessary characteristics – to being a good financial advisor that Sean lacks. For instance, understanding math and/or economics.
In sufficient/necessary terms, the argument is effectively treating computer skills and people skills as sufficient (I say “effectively” because it’s not quite doing that, because of the word “most,” but in principle, it’s the same). Recognizing this isn’t bringing in new information; it’s just noting that the argument doesn’t have all of the information that would allow it to reach the conclusion given, and that’s acceptable. On an inference question (Which of the following is most strongly supported? for instance), it’s important not to bring in new information; when the flaw being demonstrated is that the passage-writer didn’t consider everything, it’s fine to rely on that as the answer.
Treating a condition as sufficient when it’s not is effectively always a fails to consider flaw. For instance, take the following argument:
In order to become an attorney, one must pass the bar exam. Amy passed the bar exam; therefore, she is an attorney.
In the premises, we’re told that passing the bar is a necessary condition (one MUST pass the bar exam); in the conclusion, though, we treat it as sufficient, but the premises don’t tell us that it’s sufficient (just like the premises in your example don’t tell us that computer skills and people skills are sufficient). The reason that’s a flaw is that there could be other requirements (like passing the background check). If there were no other conditions, then the conclusion would be valid.
Another example: If Fluffy is a cat, then Fluffy is a mammal. True.
If Fluffy is a mammal, then Fluffy is a cat. False.
The second statement incorrectly treats “mammalhood” as a sufficient condition for “cathood,” but we know that’s false. But in terms of content, why is it false? Because there are other mammals. The statement “fails to consider” that Fluffy might be a dog, or a bat. There’s nothing about dogs or bats in the statement, but that’s still why it’s flawed. Just like there might be other things (math skills) keeping Sean from being a good financial advisor. “Math skills” are the dog or bat of your example.
On another question type, we couldn’t choose an answer on the assumption that there ARE other such skills; that would be bringing in outside information; but we can point out that the argument itself fails to consider the possibility. And we know this because the premises don’t get us to the conclusion.