That could be said about anything successful, and the word fluke wouldnt even exist...

The fact is their 'premeditation' and 'calculations' are not as accurate as you think. If you are so confident that what they intend actually happens, then why would they go ahead with the wii U? Surely they didnt premeditate and calculate a failure did they?

One day you will accept that the success of a product is based on far more things than the vision the creators have of it.

Nintendo's inability to embrace the growing "core" market is what's caused their decline. They don't appeal to third parties, their online infrastructure is lackluster at best and almost their entire 1st party line up is "kid friendly". As people often say, you buy a Nintendo home console for Nintendo games. If you aren't fond of their 1st party line up then their consoles are rather unattractive compared to their competition.

The Wii was an anomaly since it appealed to a previously non explored market. Once the "casual" market had moved on the Wii's sales started falling back towards that previous trend (one that the WiiU is now following).

Really though, the only trend here is Nintendo's unwillingness to embrace what the majority of the core market wants.

By that definition, the PS1 and PS2 could be called flukes as well then.

It means that Nintendo was unable to hold on to its non-gaming userbase it gained with Wii, they all moved on to mobile and facebook games. Nintendo tried to win them back by introducing a new gimmick: the Gamepad, but it didnt set the world on fire like the Wii motion controls.

Alas, Nintendo is even struggling to get its original userbase: the Nintendo fans to buy WiiU. Considering that Gamecube(22m) was a true hardcore gaming fan's console and catered to Nintendo fans, they are atleast aiming to get a >20 million Wii U install base.

They calculated brilliantly with Wii, and badly with Wii U, simple as that.

I have noticed that long time ago. I think that Wii's success obscured this fact to many people. Obscured it in a way that GameCube was considered an anomaly, a failure amid Nintendo's success. I tend to consider Wii Nintendo's only success within a continuing failing console maker's trend. (As OP nicely sketched out).

The fact is that Nintendo has not been able to expand its target market into which it tapped into 25 years ago. Back then, a huge NES success was due to a slew of child-friendly games which hooked in an entire generation of 8-12 year olds (and saved the industry, credit is due there). But, it seems that all Nintendo did was follow that generation and kept giving them same or siilar games, just on newer consoles. And every generation, lost a certain percentage of its followers that either quit gaming altogether, or moved onto more mature games on Playstation first and XBox later. Therefore a declining trend, in which we now, with WiiU, see the remnants of those 8-12 year olds (now 28-35 yo) that are still living their nostalgic dream through the sequels of their childhood franchises. And we see that the number has shrunk significantly, to the point that no new game can sell systems because the entire remaining target market has already purchased a WiiU, and all that's left is trying to hook some newer kids into it, but kids today much prefer to game on the go, on their smartphones, and it is very very tough to recruit 6-7 million new users, let alone get back to 60-70 million from the last century.

Wii was an anomaly, a gimmick-backed short-lived fad, hwere a ton of people jumped in to try motion controls, where they managed to bring in the entire new audience of women, grannies, family-friendly entertainment. An excellent strategy, which unfortunately was aimed at people who either grew bored of the system quickly, or just cannot be convinced to purchase a newer one that in their opinion does exactly the same thing, with exact same games and apps.

Without a new fad in sight, and without any thread of innovation or focusing on anyone but children and "middle-aged nostagics", Nintendo has no chance in today's market. Unless their new console (when and if it comes out) has something innovative and different from MS/Sony, it will sell even less than WiiU.

It lasted a normal console lifespan.

A fad would been if it died in 2009.

Or maybe, they calculated both to be successful, but one exceeded expectations and one fell short of expectations.... because of luck?

"Let's just ignore the Wii because it doesn't fit right with my theory".

Just read "The Innovator's Dilemma" by Clayton Christensen. That's the book Nintendo based the Wii on. That's the book the iPod, iPhone, iPad were based on. You may also read "The Blue Ocean Strategy" which is the strategy behind the Nintendo DS that also explains why Samsung's products took off. 

The reason the Wii U (and to some extend the 3DS) failed is that Nintendo *intentionally* stopped following these strategies. They even said that in interviews. They thought they were smart enough on their own - looks like they were wrong. In the last investors meeting Iwata talked about "finding blue oceans" again as a reaction to Nintendo's current situation. Their "Quality of Life" platform will be based on blue ocean strategy.