I'm not sure I'd even rank Watergate to be that bad as far as corruption goes. I mean, I certainly wouldn't put it on the same level as basically being in the pocket of the robber barons or Haliburton or using the office to enrich your friends and allies without regard to the law or the consequences.
There was a high degree of corruption of the Nixon administration in a number of ways, but it wasn't primarily of the 'money for your friend' variety.
Oh, he had that too - look into Bebe Robozo, for example; his former employer Pepsi was able to call him, representing 'concerned' companies with business in Chile, about the problem of a left-wing candidate, Salvador Allende, and Nixon ordered Kissinger to prevent Allende fro holding power, leading to the US coordinating a coup that the loss of Allende's life and the installation of a right-wing dictator.
But Nixon's corruption was far more broad, typically more political, and including his paranoia.
Read the following link for the type of person who did fine under Nixon:
http://www.nationalcorruptionindex.com/pages/profile.php?profile_id=520
There's evidence suggesting that Nixon, in a close 1968 election, wanting to win felt he needed to prevent the Democratic administration from success in Vietnam peace talks (ending the war was a political plus to promise - Nixon promised it, while he actually expanded the war in power), secretly communicated with the South Vietnam government to sabotage the peace talks - successfully - an act IMO of treason and murder.
There was a whole culture of political corruption difficult to capture it was so large. His 'enemies list' is infamous. He'd approve things like Cointelpro, a secret operation by the government against our own citizens on the 'wrong' side from politically. He was so obsessed with the Kennedys who had beat him as to have Senator Ted Kennedy followed and to fabricate documents implicating JFK in wrongdoing he claimed to have 'found'.
There's a reason he had people like G. Gordon Liddy, who would offer to assassinate a reporter for him, and Chuck Colson, leading a 'dirty tricks' operation.
Why so many of the scandalous and criminal figures of later Republican administrations had gotten their start under Nixon.
His culture literally had his own top organizations spying on each other, state planting people in defense and so on.
Watergate was a specific action caught and covered up, but the corruption was a lot more, as IIRC the impeachment items listed besides Watergate.
He wasn't a 'crook' in the sense that he wasn't out to pad his own bank account it seems, but rather one that corrupted the system for other reasons, such as power.