Meanwhile, the Nintendo [3]DS continues to be the #1 "game console" when you disregard form-factor, and has had nonstop YOY growth since its introduction.
The Wii U was essentially a failure because Nintendo thought there was still a market for a chained-to-a-TV console—and there is, but only in the "hardcore gamer" segment that don't care for Nintendo's games lineup. The segment who are interested in Nintendo games, have shifted to being far more interested in mobile games than TV-console games (even if they would enjoy playing those games on a TV once in a while.) The Switch is an acknowledgement of this, and that's why it's succeeding.
The Wii U was essentially a failure because Nintendo thought there was still a market for a chained-to-a-TV console—and there is, but only in the "hardcore gamer" segment that don't care for Nintendo's games lineup. The segment who are interested in Nintendo games, have shifted to being far more interested in mobile games than TV-console games (even if they would enjoy playing those games on a TV once in a while.) The Switch is an acknowledgement of this, and that's why it's succeeding.