This is nothing new to Nintendo consoles. Every since the N64 really, their games have been riddled with delays. It even affected their 2nd party developers like Rare. I think a combination of taking their time to polish everything and also smaller development teams are the reasons. For some reason I don't see Nintendo throwing 200-300 developers/artists/coders etc on one game unlike say Rockstar/Ubisoft/Activision/Naughty Dog etc. I could be wrong though.