In "The Stranger", what does Meursault mean when he says, "It occurred to me....really, nothing had changed."?

His mother's death had really changed nothing; his life went on as usual, as if nothing had happened at all.

The narrator has been through what should seem to be a life changing experience, the death of his mother. Still however he notices the same city doing the same things and he has fallen back into his same old routine; nothing has changed.