Before FBI Director James Comey was fired, the FBI investigation of Russian involvement in the US election was heating up. According to multiple sources—though denied by the Department of Justice—Comey went to the assistant attorney general to request additional resources for the investigation on Monday. Later that day, Rod Rosenstein and Jefferson Sessions visited Trump to tell him Comey needed to be fired.

On Tuesday, federal prosecutors issued their first grand jury subpoenas based on the FBI investigation. Those subpoenas “represent the first sign of a significant escalation of activity in the FBI's broader investigation,” according to CNN. That same day, Trump fired Comey.

However, according to the Wall Street Journal, the investigation was in an even higher gear than previously known—for a very, very good reason.

Mr. Comey started receiving daily instead of weekly updates on the investigation, beginning at least three weeks ago, according to people with knowledge of the matter and the progress of the Federal Bureau of Investigation probe. Mr. Comey was concerned by information showing possible evidence of collusion, according to these people.

Comey went to Rosenstein to ask for more resources, not because the investigation was going too slowly, but because the investigation was finding so much.

With his concerns mounting, Mr. Comey last week sought more resources to support the bureau’s investigation, which began last July. He requested additional personnel from Rod Rosenstein, who had been recently installed as the deputy attorney general, overseeing the FBI, people familiar with the discussions said.

And that’s when they fired him.

For everyone who was asking the question “Why now?” here’s your answer.

On Monday, Mr. Comey briefed lawmakers on his request to boost the investigation, people familiar with the discussions said. The lawmakers, who have been running their own probe of alleged meddling in the U.S. election by Russia, and possible Trump campaign links with it, asked Mr. Comey if he could accelerate the FBI investigation, said a person with knowledge of the conversations.

Senator Richard Burr, one of the few Republicans who issued a statement of concern about Comey’s firing, was getting daily updates in that last week. And while the Trump White House continues to insist that there is “no evidence of collusion,” it seems that the investigation stands on the brink of producing exactly that evidence.

To date, the inquiry has produced no “smoking gun,” these people said, but some investigators are persuaded that the evidence will show more than just casual contacts. One area of particular interest for the committee is Mr. Trump’s business dealings. The Senate Intelligence Committee has asked for information from the Financial Crimes Enforcement Network, or FinCEN, a division of the Treasury Department.

Donald Trump might dodge an investigation into Michael Flynn. He might not be harmed by a take down of Carter Page.

But if the FBI seriously looks into Baywater and Trump’s financial deals with Russian oligarchs … there’s potential for an investigation that cripples, if not ends, his time in office.