The only source in this article is the share price, all the other words are just padding with empty words and no sources to the claims.
And the share price dropping by itself is nothing new. When the original Switch was revealed (remember that iconic trailer?), share prices dropped around 7%.
So what does it actually mean? In both cases, investors are just not completely convinced this is going to make them more money. If you've been keeping tabs on the leaks, nothing new except Mario Kart was shown. As an investor, you want to have as much guarantee as possible that Nintendo will make you rich, and this reveal didn't do that.