There was a drop because most people expected a super mario bros level type of game, even though nintendo said time and time again it wouldnt do it, and because of the delay.The stocks it "lost" was probably the same stocks it gained after the news of nintendo making mobile games.Give it some time and they will recover all stocks, specially when it comes near the launch of Miimoto
My (locked) thread about how difficulty should be a decision for the developers, not the gamers.
https://gamrconnect.vgchartz.com/thread.php?id=241866&page=1