Not sure how Smash Ultimate's sales are supposed to be surprising or exceeding expectations? Even the Wii U version sold over 5 million copies on a 13 million install base, so 9 million on a 30 million consoles shouldn't be that unexpected really, especially for what has been one of Nintendo's biggest franchises for almost two decades now. Isn't this more par for the course if anything? I would have been more surprised if it didn't sell like this.
As for what I asnwered, I never thought that Monster Hunter would become such a big hit in the west, even with the more user friendly experience. I just felt that it was always going to be more of a niche series. I'm very happy it has done so well.
Look up pre-release threads, maybe you'll understand.
Some thought that because neither the Wii U or the 3DS version couldn't beat the Wii version on their own that Smash had reached the top of it's popularity with Brawl. Yeah, that was an insane Troll logic from the get-go, and many tries over and over to point that out, but to no avail. And now they're stunned silent because Ultimate is beating it's predecessors with both joycons tied.
As for the 2018 game that most exceeded retail expectations, where's Octopath Traveler in the list? Very few expected it to even reach a million sales, now it's at 1.5M, gets a Steam release and a prequel on Smartphones.