Every year the same drasha comes up over the Sukkos table. Why, oh why, does Sukkos happen in the autumn after Yom Kippur instead of after Pesach in the spring? And then one of hundreds of answers spill forth and people hide their yawns and mumble "Shekoyach!" or something along that line.
What never seems to get asked, however, is: Why do we do Simchas Torah as part of Sukkos? After all, if Sukkos needs a justification to be in the autumn since it would seem to naturally be a spring holiday, why isn't Simchas Torah part of Shavous? What's more, wouldn't restarting the Torah make more sense on Rosh HaShanah? Why read about how God remembered Sarah Imeinu on Rosh HaShanah when one could read about the creation of the world Rosh HaShanah reminds us of instead?
Amongst various reasons I've seen, two in particular caught my eye.
The first is that Simchas Torah, by its nature and name, is a holiday of happiness. Therefore, it belongs as part of Sukkos, z'man simchaseinu. The second is based on Shlomo HaMelech's blessing to the Jewish nation on the occasion of the completion of the first Beis HaMikdash (may it be speedily rebuilt after the playoffs). By timing the completion of the Torah for the end of Sukkos, this blessing can coincide with Moshe Rabeinu's final blessing to our ancestors.
While these are both good positive reasons, one must still ask why other occasions during the year don't merit the finishing of the Torah? For Shavuos, we must remember that the Torah wasn't actually given on that day. Yes we heard the Aseres haDibros on that hallowed occasion and that's why the holiday is called Zman Matan Toraseinu but the first attempt to actually receive the Torah didn't take place until forty days later and we all know how unsuccessful that was.
One might then suggest that Yom Kippur, the actual date of kabalas haTorah would be appropriate but how could we reconcile the celebrating of Simchas Torah with the solemnity of the day of repentance? Never mind the absurdity of serving the annual shul luncheon and nobody being allowed to eat it? Similarly, the judgemental significant of Rosh HaShanah precludes making that day Simchas Torah. This leaves Sukkos, with its call to happiness, to coincide with the happiness of completing the Torah again.