What's more important to them is profit.
If it makes them money (and it's worthwhile), they'll do it. Games at launch tend to sell better because there's a higher chance that early adopters will pick up other games to go along with their system, especially if it's an exclusive game that isn't a late port or has poor to mediocre reviews.
You're right about game advertisements helping...but this is where Nintendo is very poor at doing. Many negative things greatly affected this generation (including console sales, first party game sales, rushed games, games not made as well as they could be, lower scores, etc.) are Nintendo's fault.
Bayonetta 2 is a great game. It didn't have that much marketing push behind it. What's worse is that there aren't that many games similar to it on the Wii U. Bayonetta 2 shouldn't be the only game of its kind there. Whenever someone asks about other games similar to it, people usually (almost always) point to games on other non-Nintendo consoles. If you want fans of action titles to buy a Wii U, and NX or whatever other console Nintendo games, you have to have a lot more that what's usually offered. What's for them to play once they've finished it? Going the opposite directions, if Nintendo Action games X, Y, Z were there, and people were looking for more, many would most likely jump at the chance to refer Bayonetta 1 & 2, because of how friggin' fantastic they are, which in turn helps the games sell better.
Nintendo don't really make games like Bayonetta, but they could start doing it going forward. Unfortunately, they most likely won't, and for many gamers, this gives them the perfect reason, or one of many, to not care about Nintendo consoles, and many of those reasons are why the Xbox One and PS4 are both outselling the Wii U.
This is, to me and lots of other people, why a high volume of GOOD 3rd party games are so, so, so important to the success of any platform and the happiness of its user base. Check out the library of the NES, SNES, PSOne, PS2, GameBoy, DS, etc., etc. It clearly shows that this is one of the key reasons why people buy video game consoles...period.
I'm not about loyalty. I'm not blind fan who buys into everything my "favorite" company says and does. If the NX doesn't have the games or has other technological and physical problems, not many people, including myself, are not going to buy it.
Bayonetta 3 on the NX should be one of many games like it on that system -- not just the only one. If not funded by Nintendo, and if the NX turns out to be far under-powered compared to the other consoles, if a multiplatform Bayonetta 3 is made, expect it to follow the trend of being only for PS4 (Neo), Xbox One (Scorpio), and PC.