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.
People are surprised not because of that big number but the timeframe of that number.
25 days of sales = 9-10m(Physical+Digital)
Smash Ultimate is already outpacing the previous entries and about to overtake the best selling version in just a month.