You can read it here.
From the Factual Proffer:
When the defendant lost the 2020 presidential election, he resorted to crimes to try to stay in office. With private co-conspirators, the defendant launched a series of increasingly desperate plans to overturn the legitimate election results in seven states that he had lost—Arizona, Georgia, Michigan, Nevada, New Mexico, Pennsylvania, and Wisconsin (the “targeted states”). His efforts included lying to state officials in order to induce them to ignore true vote counts; manufacturing fraudulent electoral votes in the targeted states; attempting to enlist Vice President Michael R. Pence, in his role as President of the Senate, to obstruct Congress’s certification of the election by using the defendant’s fraudulent electoral votes; and when all else had failed, on January 6, 2021, directing an angry crowd of supporters to the United States Capitol to obstruct the congressional certification. The throughline of these efforts was deceit: the defendant’s and co-conspirators’ knowingly false claims of election fraud. (p. 3)
See that? It says, "knowingly false claims of election fraud."
And now with some facts:
Although his multiple conspiracies began after election day in 2020, the defendant laid the groundwork for his crimes well before then. Leading into the election, the defendant’s private and Campaign advisors, including [P6] (then a private citizen) and [P2] (the defendant’s Campaign manager), informed him that it would be a close contest and that it was unlikely to be finalized on election day—in part because of the time needed to process large numbers of mail-in ballots prompted by the COVID-19 pandemic. They also told the defendant that the initial returns on election night might be misleading—that is, that he might take an early lead in the vote count that would diminish as mail-in ballots were counted because his own supporters favored in-person voting, while supporters of his opponent, Joseph R. Biden, favored mail-in ballots.
Privately, the defendant told advisors—including [P6] Campaign personnel, [P7] (a White House staffer and Campaign volunteer), and [P8] (the Vice President’s Chief of Staff)—that in such a scenario, he would simply declare victory before all the ballots were counted and any winner was projected. (p. 5)
And then:
By October 2020, [P1] a private political advisor who had worked for the defendant’s 2016 presidential campaign, began to assist with the defendant’s re-election effort. Three days before election day, [P1] described the defendant’s plan to a private gathering of supporters: “And what Trump’s going to do is just declare victory. Right? He’s going to declare victory. That doesn’t mean he’s the winner, he’s just going to say he’s the winner.” After explaining that Biden’s supporters favored voting by mail, stated further, “And so they’re going to have a natural disadvantage and Trump’s going to take advantage of it—that’s our strategy. He’s going to declare himself a winner." (p. 7)
Immediately following election day on November 3, the defendant did exactly that.
According to Newsweek, P1 is Steve Bannon.
They knew they'd lost.
