You cannot deny, though, the momentum that the Switch built from launch onward was credited to Breath of the Wild. More people bought Breath of the Wild than Switch units when the console first launched. That was mainly due to the low supply the Switch had once it launched, and Switch sold over 2+ million from March to April (or was it May?) in 2017.
I never denied that, simply stated that BotW wasn't a killer app for the Switch. It was a killer app for Nintendo, and Switch was just the objectively better option.
In other words, it was a killer app for the Switch.