How long did it take for evidence to be found on Nixon?
Well, the DNC was broken into June 17, 1972.
March 17, 1973: Watergate burglar McCord writes a letter to Judge John Sirica, claiming that some of his testimony was perjured under pressure and that the burglary was not a CIA operation, but had involved other government officials, thereby leading the investigation to the White House.
May 19, 1973: Independent special prosecutor Archibald Cox appointed to oversee investigation into possible presidential impropriety.
July 23, 1973: Nixon refuses to turn over presidential tapes to Senate Watergate Committee or the special prosecutor.
October 20, 1973: "Saturday Night Massacre" - Nixon orders Elliot Richardson and Ruckleshouse to fire special prosecutor Cox. They both refuse to comply and resign. Robert Bork considers resigning but carries out the order.
November 17, 1973: Nixon delivers "I am not a crook" speech at a televised press conference at Disney World (Florida).
April 16, 1974: Special Prosecutor Jaworski issues a subpoena for 64 White House tapes.
June 15, 1974: Woodward and Bernstein's book All the President's Men is published by Simon & Schuster (ISBN 0-671-21781-X).
July 24, 1974: United States v. Nixon decided: Nixon is ordered to give up tapes to investigators.
May 9, 1974: Impeachment hearings begin before the House Judiciary Committee.
July 27 to July 30, 1974: House Judiciary Committee passes Articles of Impeachment.
August 9, 1974 Nixon resigned the presidency.
In case you don't remember the time line,
Timeline of the Watergate scandal.
So, it didn't happen over nite.