I am starting to think that Lord Voldemort planned to commit suicide by proxy. Being without any personal aims, totally bored, without any happiness, surrounded by idiots, no chance of improvement - yet he cares about the world, at least somewhat, and realized that the original plan of playing chess with Harry would not alleviate his mood anymore anyway. And he has a better, happier and (age adjusted) more intelligent clone running around, so it is not like he will cease to exist altogether.

So he told Harry where to find Memory charms, prepared the plot, got the Stone (for Harry), made Harry take the Vow to keep his recklessness in limits, let him keep his wand and put him to the Final Exam.

The problem is that if he planned to be Obliviated, the plot was extremely complicated and relied on too many factors that could have gone wrong. So perhaps LV just threw the towel and said to himself, darn, let's Harry try whatever he can think about to do with us, and if he fails, well, it's not like I cannot try something else in some decades.