Oh boy. Well, the invasion army was apparently small-ish, since otherwise the Khitan capability to wage war and win against the Islamic states of Central Asia would have been greatly hampered. Dashi was confident of his martial prowess, yet he did not go east himself. The commander was not demoted despite this failure and continued to thrive in the Kara Khitai empire. Dashi made no attempt thereafter to regain the east, even after the west was pacified. He shows few signs of caring much for regaining the east, whether he had practical reasons to do so or not is beside the point.
The most widely accepted theory is that the 1134 attack was for homesick contingents of the Kara Khitai and that Dashi himself had no particular attraction to the east as opposed to a new western Khitan state. I believe UNESCO suggests that Dashi may have thought that he would be more famed and successful by creating a new empire than trying to regain an old one.
I acknowledge that Yelü Dashi might not have cared about China. I'm just not convinced that it's the only reasonable explanation. Yes, the army he sent was probably small (but even if not 70,000, it might still have been a significant force). Maybe he didn't want to risk his entire army in one invasion. Sure, he didn't demote the army's commander. Maybe he found the commander too valuable to demote, given how he continued to promote him. Yes, he didn't lead the army. Maybe it was because he didn't want to be captured by the Jurchen Jin a second time. There are many reasons behind Yelü Dashi's actions, and indifference is just one of them. It's perfectly possible that Yelü Dashi wanted to reconquer the Liao territory, but he never got around to it because he was busy securing the Kara Khitai territory. All of the practical reasons I mention could help explain why he never made a full-fledged attempt to defeat the Jin even if he had a desire to do so. Unless archaeologists find an edict from him saying "The Western Liao will no longer try to conquer the east," we can't say what he thought or didn't think.
I can think, for example, of a post-1900 Chinese regime that definitely wanted to reconquer China, but it had no capability to do so, and therefore it never embarked on a large-scale military campaign. I would not say this regime "didn't care about China." It cared, but its actions were constrained by contemporary realities. The same might have applied with the Kara Khitai.