Reverse Psychology

There is something utterly strange about the sequence of events in which Moses passes the Torch to Joshua. It is preceded by the mitzvah of hakhel; men, women, children and converts assemble in Jerusalem where the King reads from the holy Torah in a ceremonial way intended to invoke the greatest awe and splendor - to the point where the Jewish people are no less than guaranteed that were they to keep the mitzvah, they will surely fear God, along with their progeny in the promised land. 

Immediately thereafter, Hashem tells Moshe to summon Joshua, and tells Moshe in no uncertain words that the same way a husband may act promiscuously and unfaithfully, the Jewish people will likewise stray. The question thus is what happened to the promise, and to what extent does this momental gathering have an effect if its message isn't adhered to?

Is there something diabolical in making a promise that will inevitably not be kept? Or, were there other conditions that the promise was predicated on?

It would seem to be that reverse psychology is being employed on two levels here; for one, for the nation to come with a pureness of heart, they need to know that there's a fullness of spirit and faith that can guarantee their success - for those with young children, getting them to shul to hear the shofar is hard enough! To pack up the whole house, lock, stock and barrel and make an exhausting journey that could take weeks was no small order. But at the same time, unlike other faiths, indulgence cannot be bought; the Christian way of buying penance not only doesn't work, but corrupts you, so therefore, the essence of hakhel was to come, open your heart, and if the nation as a whole would do that, surely their children would walk in Hashem's path. The reverse objective is thus achieved, in stark contrast to a half-hearted, half-baked promise that offered far less. 

That notwithstanding, perhaps in a form of self-handicapping, setting the bar low so that the leader wouldn't feel accountable for the people's failure, Moshe, and likewise, summarily, Yehoshua are warned that the people will return to their errant ways, but that will not, in any shape or form diminish from your success as parents. The same is said in many respects about parenting; we're responsible for our efforts, but not the results, resonating the teaching in the Talmud (Moed Katan, 28.) that "long life, one's sons and livelihood are not the result of one's merits, but rather, one's good fortune."