What game contributed the most to Switch's record breaking success

[Chrkeller]

Ashadelo said:

It was the fact that it was both portable and a home console. I dont think there was one particular game, as Nintendo has many many IP's that sell insanely well. Don't forget SMO is the highest selling 3D platform of all time. That's no small feet

This.  It sold because of convenience.  The world has moved to convenience via Spotify, Steam, Netflix, Amazon, etc.  Nintendo capitalized on the convenience trend with the S1.