They're a law firm that specializes in _patents_. When all you have is a hammer....
Also, presumably you failed to register your software with the copyright office before the infringement began. In such a case you're less likely to get a fat damages award. Which is actually a good reason to pursue a patent claim, but if we're being cynical it's also a good reason for a firm to _prefer_ a patent claim.
The fact of the matter is that if the case was a slam dunk as you say, you should have been able to get an injunction fairly quickly, depending on when this occurred. Step one to seeking an injunction would have been to register your software (or a component of the software, if you didn't want to divulge the whole thing) with the Copyright Office. Currently their e-filing website says it'd take 6-10 months. It used to be much shorter than that. A few years ago, IIRC, I received a certificate in less than 90 days. In any event, that's much shorter than 2 years.
It's also a good lesson: always register at least some component of your software with the Copyright Office; a component that an infringer would necessarily have to copy. To get through the courthouse doors you need a certificate from the Copyright Office, but it doesn't have to cover the entire, larger work. It's more of a procedural hurdle of the copyright statute that courts construe very liberally, so you needn't be afraid of having to publish all your source code just to get a certificate.
The nice thing about copyright is that it's simple enough that you don't really need to involve a lawyer. Of course, you don't do this to the exclusion of any patent filings, but it's a smart move that is almost zero cost. Paste your software into a TeX document, generate a PDF, and upload it to the Copyright Office website. Easy peasey.
> They're a law firm that specializes in _patents_.
What the fuck. Oh, you got that when you googled them, and you think the fucking top-tier national IP law firm had no other ideas at all because the patent hadn't issued yet.
