You could say they follow the same trends, but then you don't seem to truly understand, so I've included the 360 to make it more obvious.

The trends that the Wii U and 3DS followed, that you suggested the 3DS was helping the Wii U are the holiday seasons, the defacto best time for console sales. Or would you suggest that the 3DS helped the Xbox 360 sales as well?

In fact, if the 3DS was helping the Wii U, the Wii U should have exceeded it seeing as A. the 3DS had already peaked and B. the Wii U started in the holidays not to mention C. its second holiday did much worse.

The 360 and 3DS sales in the holiday seasons almost match, an obvious example of how they didn't really compete against each other. At the same time, the Wii U being much lower during those periods suggest that they are competing, against both the 3DS and the 360.

And sure, you could suggest that all the consoles on the market are the Wii U's worst enemy. But the 3DS is the only other console on the market getting Active Development and Platform support from Nintendo. So unlike those other platforms, barring the Wii since it about to be discontinued/already has been in some places, the 3DS harms it by competiting with it both on the commercial front and inside Nintendo's.

As for all the Allegations that Wii U is its own worst enemy, that doesn't make any sense. Not only is the Nintendo responsible for the dearth of games and system sellers on the Wii U, they put them on the 3DS to add insult to injury, price cuts have not helped, games have not helped, even if you suggest it was the Wii U tablet that rose the price, its Nintendo who made its development integral, and now not having a Wii U tablet in many games makes players miss out on some crucial features.

Nintendo has obviously fucked the Wii U, but as long as they continue to support the 3DS over it, it doesn't even have a ghost of a chance of pulling any reasonable sales.

And that blue circle is Mario Kart 8.

Because one is a game you play on a tiny screen with a significantly less powerful system, and another is something you play with a controller and an HD system on your couch with a huge TV?