[nvm0n2]

He was checking if you understand what the actual benefits of trading firms are to the wider market participants. I've never worked in trading and even I know the answer to that: he was looking for a discussion of the value of liquidity and price discovery.

Sounds like you gave an answer that didn't mention that at all, and may have presented the firm as merely taking advantage of other people's mistakes to make profit. Clearly that's not how he saw it, and the VP correctly guessed from your social media that you may not actually have understood the part of the finance industry that you were applying to work for. The question was to check whether you'd actually be enthusiastic about the work you were doing and you did indeed fail it.

This would be like if you turned up at Google and an interviewer said, "What do we do here" and you said "exploit data to profit from people's ignorance" and when they gave you a second chance you couldn't answer.

Frankly you can't get a job at most firms if you can't explain why you think the company should exist.