A short lifetime ago, back in the earliest days of the pandemic, and around the time that Tom Hanks announced he had Covid-19 and the N.B.A. upended its 2020 season, I started talking to one of the most powerful financial minds on Wall Street, a leader in every sense of the word. For the purpose of this article, and for future emails, I will to refer to him as Mr. Big, which sums him up pretty nicely. I will be interviewing Mr. Big about the most important issues on Wall Street, from time to time, over the coming months. (For those of you who enjoyed my interview last week with Jamie Dimon, all I will say is that he is not Mr. Big, although he is a very important person on Wall Street. But no more hints. Sorry.)