If I had to guess, in the general sense: when you run your mouth to the point of making legal threats, the person or firm you're threatening will start actual legal proceedings themselves because they think (or know) you're full of shit.

It's worth noting that that's not at all what Newegg claims happened.[0] So "accidentally" in this case is probably more accurately states as biting off more than one can chew.

[0]: https://www.newegg.com/insider/patent-trolls-learn-mess-newe...

> How could they have accidentally sued someone?

I think the poster meant "accidentally targeted someone who would not only fight back, but also hurt the patent troll", not "accidentally filed a suit".