Lawyers from Brigade and Citibank calculate Brigade's odds of winning. Let's say both sides agree it's 5%. That means the expect returns on litigating this are $8.75 million to Brigade. The cost of litigation is $2 million. The two sides discuss. They settle for anywhere between $6.75 and $10.75 million, depending on who negotiates better. That's where neither side wants to litigate.
For being a little bit douchey, Brigade walks out a few million ahead.
If sides can't agree (e.g. Citibank lawyers estimates 1% odds of winning and Brigade 10% odds), they go to court. But 9 times out of 10, it's a settlement like that.