Previous user took a very huge risk. I've seen similar stuff happen, you can get sued (along whoever told you, but you need proof) just for the sake of making an example in front of the rest of the company.
Also, still it is not illegal. Just that the shareholders need to sue him to matter at all.
That said, I think it'd be a pretty tough argument to make that an employee following the instructions of their superior was breaching fiduciary duty. If they weren't acting to their employer's benefit, then whose? Employee fiduciary duty cases tend to be more about things like embezzling or competing with your own company while you're still working there.
An example of Fox getting shut down for trying to claim that sexual harassment was a breach of fiduciary duty: https://www.barnespc.com/news-articles/limitations-on-the-sc...
There has to be proof about that. If everything was verbal how do you prove it?
There's no way around the fact that sabotaging your company is illegal and a breach of contract.