Nintendo made 6 million fewer Switches this year because they just couldn't find the necessary semiconductors to build all 30 million they'd planned to, and similar supply problems have led to PS5s and Xbox Series X|S flying off shelves faster than either Sony or Microsoft can produce them.
If I had to guess, I'd say it has something to do with the ongoing global chip shortage which has led to stock shortages of pretty much everything. A message on the Nintendo website writes: 'More controllers will be available in 2022.' No further details were provided. Not only did the objectively worse controller out-sell the Genesis gamepad, but it's also going to remain out of stock until next year. Meanwhile, the Genesis Switch controller is still available, although we don't know for how long.
That's right, what everyone said was the worst controller ever has gone out of stock again after initially running out soon after the N64 Switch Online expansion's arrival. Nintendo's N64 Switch controller is out of stock.