There are all sorts of directions he could have gone from here, including him deciding that the world seems particularly hateful and so why not keep up the villain role, when the benefits are so much better? But spending a few years in an "okay, now what?" slump seems out of character.

Yeah, I get that now.

I've amended my suspicion to be that Riddle enjoyed himself in the Voldemort role, for maybe a little less than eight years. I still think he intentionally left the stage and didn't somehow end up on the losing end of a Nuts roll vs.. infant. Tom Riddle bites it in a cutscene? Lame.