Nintendo and Youtube.

Ah, but you are redistributing parts of it. Specifically the images (and probably music). This is in part why most Nintendo games (and probably nearly every game) at the end of the credits say something along the lines of "All rights, including copyrights of Game, Scenario, Program, Music are property of nintendo".

Simply uploading a rip of the game files isn't the only way to redistribute parts of the game which (Apparently) legally belong to nintendo, whether you own a copy of the disc or not.

I'm not arguing it isn't a plantain move (absolutely is), but still, like everything, the goal of a publisher is to get as much of your money as possible while actually given you as few rights as possible.

But it is plausible that at the end of the day they turn out with less money because they lost this free advertising of let's play. Therefor attempting to gather more money, yields them with less.