Not necessarily. It certainly helps the Switch, and it's cool to play third-party games in handheld mode. But there wouldn't have been much third-party support if the console didn't sell on the strength of first-party games. The Wii U was overpriced, tough to develop for, and the first-party games did not excite to the level Nintendo hoped. Third-parties mostly jumped ship by 2014, but that wasn't the biggest reason Wii U tanked.
It's great for players and companies for Switch to have good third-party support, but it's not one of the biggest reasons Switch is a smash hit.
Lifetime Sales Predictions
Switch: 151 million (was 73, then 96, then 113 million, then 125 million, then 144 million)
PS5: 115 million (was 105 million) Xbox Series S/X: 57 million (was 60 million, then 67 million)
PS4: 120 mil (was 100 then 130 million, then 122 million) Xbox One: 51 mil (was 50 then 55 mil)
3DS: 75.5 mil (was 73, then 77 million)
"Let go your earthly tether, enter the void, empty and become wind." - Guru Laghima
