You do realize that Greene and the DA have likely been in discussions well before these things were resolved? The case wasn't weakened by it. They probably knew that Greene was attempting to settle and waited til that was resolved before doing the plea deal. I imagine one wasn't going to happen without the other. Settling the civil side didn't necessarily preclude settling the criminal case though.
How do you know this? A DA has a large number of cases they deal with at any given time. Of course Kamara's team did what they could to get the best outcome possible, and it worked out that they got a plea they could live with.
DAs are always looking to offer plea deals. I have no doubt they traded offers well before they finally came to an agreement. That's really not surprising. Neither side wanted to go to court because of the risks involved, so they're going to try and settle as over 90% of all cases do.