De Mambo dev had no interest in bringing the game to Wii U, Nintendo reached out to them for Switch version

Coming from a Eurogamer interview with dev Shaun Roopra...

We tried to avoid Nintendo. At that point it was the Wii U so there was no point, it was dying off. And they had Smash already, so... At the beginning it was the Vita, which we thought was perfect because it was so minimal. We tried to avoid Nintendo, but then they came to us, so what are you going to do?

We thought it was for the Wii U, so we were like 'nah, we don't want to do the Wii U'. Then they mentioned it might be for NX, and we realized from Eurogamer's rumours that maybe it's true - maybe that is the NX!"

from GoNintendo