Adam Davidson at the New Yorker explains why immunity for Weisselberg is such a big deal.

In late 2016, I had lunch with a former high-ranking Trump Organization executive, a person who said he was happy to share dirt on his old boss, but who confessed to not having much dirt to share. This executive wrote a list of people whom I might contact to find out about anything potentially illegal or unethical that Donald Trump may have done. At the bottom of the list was the name Weisselberg. “Allen is the one guy who knows everything,” the person told me. “He’ll never talk to you.” I have had nearly identical conversations with different people who work or have worked for the Trump Organization many times since. They all described his role similarly: Allen Weisselberg, the firm’s longtime chief financial officer, is the center, the person in the company who knows more than anyone.

And he won’t talk to you…until now and “you” are prosecutors.

On Friday, the Wall Street Journalbroke the story that Weisselberg had been granted immunity by federal prosecutors in the Southern District of New York so that he could share information in the investigation of Michael Cohen, Trump’s former personal attorney and dealmaker. It is safe to say that the entire world of Trump watchers—those journalists, political folks, and advocates who carefully monitor every bit of Trump news—went bonkers. Weisselberg is the man who those people most want to speak. He is also the man who has, for decades, been the most circumspect.

As the C.F.O., Weisselberg tracked the money that came into the Trump Organization and the money that went out of it, former employees told me. I often found myself wondering what the Weisselberg part of the operation looked like. (I called and e-mailed him a few times, but, not surprisingly, never heard back.) Some told me he had a couple of bookkeepers, but that he personally handled most of the paperwork. Weisselberg knew who was paying or lending money to Trump, and he knew to whom Trump was giving money. When Trump became President, he placed his business interests in a revocable trust overseen by his son Donald Trump, Jr., and Weisselberg.

He knows where allllll the bodies are buried.

Since one of the Mueller investigation’s core aims is to understand whether the Trump campaign worked with Russia to sway the 2016 Presidential election, Weisselberg now seems to be a key witness. Worse, for Trump, if Weisselberg, fearing prosecution himself, tells prosecutors of other criminal activity in the organization, that information will likely be referred to other federal and state prosecutors, thus broadening the investigation of Trump’s business.

I wonder if it’s occurring to Trump about now that it wasn’t such a hot idea to run for president after all. It looks as if it could turn out that doing so got him and his children in a world of legal trouble, which wouldn’t have happened if he’d just gone on being a lying cheating thieving real estate swindler.

There are many open questions about how precisely the Trump Organization has made and spent its money in recent years. There is, for example, a question about where Trump got more than two hundred million dollars in cash to buy and lavishly upgrade a money-losing golf course in Scotland. In a deal in Azerbaijan, Trump knowingly did business with a family that is widely suspected of laundering money for Iran’s Revolutionary Guard. The F.B.I. has reportedly investigated the source of funds for a Trump-branded property in Vancouver, Canada; the Trump hotel in Toronto also has suspicious funding. These are just a handful of the many business deals that Trump has conducted that have signs of possible money-laundering, tax evasion, sanctions violations, and other financial crimes. Many of the key questions about Donald Trump revolve around his funding sources and his business partners: Did he knowingly receive funds from criminals? Did he launder money for criminals? Did he receive remuneration to look the other way when his partners broke the law? Was much of his business built on selling his famous name to make illegitimate projects seem viable? More broadly, where did his money come from? Where did his money go? And how much questionable activity has he hidden from the world? Trump himself may not know the exact answers to all of these questions. Perhaps Allen Weisselberg does.

…

There are now multiple investigations of the Trump Organization being conducted by special counsel, Robert Mueller, the New York Attorney General, the New York State Department of Taxation and Finance, the Manhattan District Attorney, the Southern District of New York, and—quite likely—other jurisdictions. President Trump is unable to stop most of these investigations. With Cohen and now Weisselberg providing information, it is becoming increasingly certain that the American people will—sooner or later—have a far fuller understanding of how Donald Trump conducted business. That is unlikely to go well for him.

Small consolation for all the damage he’s done.