If you're more interested in the journalistic perspective, check out Lily Haight's podcast on how Watergate changed journalism.
What happened: "Tapes revealed that President Richard Nixon and his top advisors were involved in covering up a break-in at a Democratic National Committee office in the Watergate complex in Washington, D.C. Nixon resigned before he could be impeached, becoming the first President to step down. Several of his top advisors — including the White House lawyer, Chief of Staff and Attorney General — did prison time."
Why it was so scandalous: "The Committee to re-elect the President was 'using mechanisms of government to attack domestic opponents in the press and the political world, even breaking into the psychiatrist’s office of the Pentagon Papers leaker, Daniel Ellsberg, to see what kind of dirt they could use to smear him,' Perry explains. 'That’s antithetical to what the country is supposed to stand for; we’re supposed to be a government of laws, not of men. Here is a president defying the law and breaking the law and the Constitution to secure a victory in 1972 — which they did, that part worked. It engaged all three branches of government, two of which countered the President and stood up to the scandal, and the fourth estate played a very large role.'"