It might be that they made a game like this to get familiar with the Wii controller, but i dont think its the main reason. If it was, then they could just make a mini game collection or something that would take less time and be more cheap to make.
Z&W is not just a shovelware game, it seems they have put some time and effort into it. If they didnt have faith in the products they were making i dont see why they would make it. I belive that Capcom thought this would be a great hit to be honest. As said, they game looks to have great potetinal in selling many copies.
However, this is only 1st day sales, i'll wait for the full week numbers. It might be somewhere between 15-20k. I dont know exactly how much that was expected from this game in terms of sales, but from what i've read and the hype i've seen i would think it would sell more atleast. This is also just Japan, it might do much better in the west and some/much profit could be made