Woodward and Bernstein were already investigating (for many months prior to the crash), and Nixon's later coverups (after March 1973) don't seem to be connected to the crash in any way.
Perhaps if the crash hadn't happened, the people/money on board could have ensured McCord (and the other plumbers) would have stayed quiet instead of telling Judge Sirica that it was a White House operation. Without some significant evidence of intent for the passengers, though, this is a pretty soft argument.
> What’s clear, though, is the influence the crash had on the arc of the Watergate scandal. It was a crucial turning point. Howard Hunt, worried his children would be orphans if he spent years in prison, asked his lawyer to meet with Colson and request a pardon from Nixon after a year of incarceration if Hunt would plead guilty and avoid trial.
> Colson spoke with Nixon, as recorded in White House tapes. Nixon agreed to the clemency proposal.
> Four other Watergate defendants, Cuban Americans from Miami whom Howard Hunt had brought to the burglary operation, took this as a cue that they’d be pardoned, too, and also pleaded guilty.
Perhaps if the crash hadn't happened, the people/money on board could have ensured McCord (and the other plumbers) would have stayed quiet instead of telling Judge Sirica that it was a White House operation. Without some significant evidence of intent for the passengers, though, this is a pretty soft argument.