They also got to keep their new Ayatollah and continue with their religious government. An escalation of the war would have certainly ended with a complete regime change. Which would have been very expensive in life (Iranians) and money (Americans).
There was never going to be a regime change. Continuing the war meant many Americans were going to die (in addition to bankrupting the US). I'm a US citizen and very glad Iran came out on top here.
Their new Ayatollah is braindead. It's not over yet.
A complete regime change would probably only come with a large scale invasion, bigger than Iraq's. A huge majority of Americans don't want that.