I think Tracy Watkins is wrong when she claims:
The letter that sank Nick Smith’s career was nowhere near as damning as the one that Prime Minister John Key was prepared to let slide just a day earlier.
The second letter makes reference to two other National MPs disclosing a conflict of interest, which Smith fails to do, and he also omits to mention his relationship with Pullar.
But I suspect the decision to sack Smith was made when Winston Peters announced it was a sex scandal, and Smith then refused to comment on his private life, a development that tipped the balance against him.
It was an odd chain of events that led to this: Smith had a relationship with Pullar, who then devoted herself to a vendetta against ACC, a department Smith then became the Minister of, which then sent Pullar thousands of confidential case files (under circumstances that are still very murky), which Pullar evidently confronted Smith with in an attempt to reach a settlement.
The settlement obviously didn’t happen, so Pullar leaked the patient files to the media. Pullar’s name was leaked to the media as punishment, either by ACC or their new Minister, Judith Collins, and it’s not hard to guess which of the two is more likely to dish out this sort of punitive vengeance. Presumably Collins was unaware that Smith had intervened in Pullar’s case.