I remember after E3 2012 when many people on this forum thought the Wii U would do amazing because of its appeal to Hardcore and Casual. Then the sale numbers came out, and we found out it appealed to no one but hardcore Nintendo fans. (Actually, it didn't even do that right. I didn't get one until 2015.)
There are many theories on why it failed. But I can say the Switch succeeded because Nintendo made a system to appeal to all their young, old, and new fans. They also cheated by combining two systems into one.