Typically by virtue of being a whistleblower, you're throwing your career under the bus. That alone lends you more credibility, especially when you hold a position like she did.

Plus as someone else said, there have been plenty of whistleblowers this election cycle, all of whom were immediately claimed as being disgruntled workers, partisans etc no matter how professionally they tried to handle it. At a certain point we really need to start putting the burden of proof on the state and governmental agencies rather than playing defense for them.