Nintendo offsets lackluster hardware with exceptional games. The end result is Nintendo rarely becomes the outright leader in any hardware segment. I agree they are successful, but I can't recall when they last "blew away the market"
5 out of the top 10 consoles sold of all time are Nintendo. They are the outright leader and always have been in handhelds and the Switch has been the best selling console for the past 2 years
In the past 2 years, Sony has been cannibalizing the PS4 with the PS5.
Nintendo is the only major player in the handheld category: of course they're a "leader". The success of the Switch supports my prior point: it's a warmed-over Nvidia Shield that has very mediocre hardware (Tegra X1 - Maxwell arch), but has amazing first-party games on it. BoTW is one of the best games I have played.