Here's the problem - the accusation was already public thanks to the criminal charges. At that point, if I am innocent, I wouldn't pay the accuser who was trying to sully my name one dime. I would be in the media as much as possible to proclaim my innocence. If there were a civil trial, I would fight it every step of the way. My name and reputation have a worth far beyond 25K or $1M. Because, like it or not, once my career would end, my name and reputation do not. That endures.
It was a tougher decision than that, I bet. There was probably good reason to think that letting the court case drag out would cost him much more than $1MM in the form of opportunity cost on a next contract.
Then there's the idea that the NFL probably didn't relish the thought of another long, drawn-out DV case for a star player in the media at that time. Who knows what sort of pressure they applied, but even in the form of a suspension, they could make it very expensive for him or even potentially prohibitive enough that teams might not go through the hassle of signing him and waiting out the suspension.
Hardy's pretty much said from day one that he is innocent of laying hands on her, but guilty of bad judgement in a number of ways for being in the situation in the first place. The night in question, he wasn't the only person in the room. The marks are significant, but they're not the results of a beating (at least to me they look like marks from restraining or squeezing a person).
There's really just no way of knowing what sort of dysfunction happened in that situation. No party is credible. All parties have financial reasons to lie. All the stories conflict. At some point you just have to throw up your hands and give up trying to sort it out.
Either way, he's obviously done in Dallas, and probably done in the NFL. Whether that's because he hit a woman or because he handled a dumb situation like an idiot, it hardly matters that much anymore. He's now an object lesson in what not to do with a promising NFL career.