Investors really fell for the mobile hype.

Nothing really alarming, is the way of stocks..

It's not really hype. Nintendo is likely to make a ton of money from mobile. It's just that the market is scared shitless right now due to a very uncertain economy and sitting in Nintendo stock when those mobile profits may take a little longer to come to bear fruit isn't what scared investors want. They want something safe, probably something that gives them good dividend returns right now, because everyone is on pins and needles. 

I still would say Nintendo is a decent-to-good investment long term because I do think they will do very well with mobile. But the best time to buy was in 2014, not now, it's still way higher than it was back in that down period. 

It'll go way back up once Pokemon GO hits the market

Unsurprised. I might invest in the future because I see the actual potential in this and not one involving Super Mario Mobile

No wonder, they delayed what was likely to become their most profitable venture in years and are being hammered by reports of slow sales globally. Change in management doesn't really inspire confidence either, in many cases, the new CEO has a ways to go before he can start working for real and have an impact for the future.
It was expected, should go up again once the mobile operations are up and running, by how much depends on how well they do, of course.
Any and all NX news could affect stocks as well, for better or for worse.

Did the wiiu anouncment and eventual release do that ?

If its some weird product it can casue the stock to drop.