Are you sure you understand it? Insider trading is not limited to employees, that's a common misconception.
I don't know the German law on the matter, but I would wager that the prosecution was warranted, even when the court ends up determining that the charge doesn't hold.
You definitely do not understand the word, because it is not limited to people, the word "insider" is limited to the information: is the information publicly available? If the answer is "no", then it is "inside" information, and trading on it is "insider trading".
These short sellers were trading on publicly available information. They just gave this information more publicity after getting their short positions, which is what you should do if you discover a market inefficiency that nobody else has discovered yet. That's your reward for making the market more efficient.
BaFin claims that this is insider trading was BS then and is BS now. They just don't understand how markets work, what their job is, and as a consequence did a poor job.
> These short sellers were trading on publicly available information.
We're talking about positions that were opened right before the FT article was published. The FT article included allegations by an insider, it wasn't only public information.
Granted, there was also publicly available circumstantial evidence that things were fishy at Wirecard.
Either way, these short sellers weren't convicted, that doesn't mean they shouldn't have been investigated.
The earliest article I can find from the FT that references insider allegations of fraud is https://www.ft.com/content/03a5e318-2479-11e9-8ce6-5db4543da..., which was published almost three years after the report referenced in the Yahoo article. What article was this supposedly timed with?
I don't know the German law on the matter, but I would wager that the prosecution was warranted, even when the court ends up determining that the charge doesn't hold.