Strange said he had no purpose, but he found it thanks to Arabella. But 2B isn't here and she is the same as him: an android made to serve the humans on the moon, drifting aimlessly if severed from that goal. There will be no answers there; she is his reason for living but not his purpose.

9S lets out a hollow laugh. "Is that how you did it? You looked for purpose and found it yourself?"

He'd joked with Strange about being useless after the war is over, but faced with the reality of turning his back on the war and finding a new reason to be terrifies him. Is this what the other androids felt before they deserted? And in the end 2B and him had cut then down for it. Without the guarantee of 2B with him, there's only terror thinking about turning away.