If he felt any curiosity he was entirely unconscious of it; it was dormant if it existed at all.

As he was able to consider her dispassionately he knew that he had not come to look at his mother's grave.

She had been nothing to him, his heart did not beat a bit faster when he thought of her.
Then, why had he come?
He did not know or care.

Had he been a psychologist he might have attempted to frame reasons, building them from foundations of high-sounding phrases, but he was a materialist, and the science of mental phenomena had no place in his brain.
Something had impelled him to come and here he was, and that was reason enough for him.

And because he had no motive in coming he was taking his time.