While it's still believed to have been leaked ahead of schedule, apparently that's not exactly how the story goes. In the official press release, the Switch version is described as being a "happy mistake". A clerical error essentially showed there was interest in a Nintendo version, so the team decided to give it the greenlight.
Here's the story in full, courtesy of the Warhorse PR:
"Kingdom Come: Deliverance for Nintendo Switch was born out of a “happy mistake.” At the end of 2020, the Kingdom Come: Deliverance Royal Edition was announced for the PlayStation 4 in Japan. Due to a clerical error, the game was also listed for the Nintendo Switch, which at that time was not in the plans. The ‘mistake’ was fixed right away, but the information spread. However, the overwhelming feedback was eye-opening and an integral part in decision making later. Saber Interactive, also a legacy studio of Koch Media, has proven on multiple occasions that they are the right partners for this endeavor to make the unthinkable thinkable, and were tasked with bringing Kingdom Come: Deliverance to the Nintendo Switch."
Warhorse PR Manager Tobias Stolz-Zwilling goes on to state how the worldwide interest in a Switch version made Warhorse "reconsider" its opportunities:
“It is amazing to see how much involvement and influence gamers worldwide can have on game development. The overwhelming feedback and fan reaction made us reconsider our opportunities and made us sit down with Sabre Interactive, who is the perfect candidate for this ambitious undertaking"
Saber Interactive has already proven itself as one of the top Switch port specialists. It also made the impossible possible with the release of The Witcher 3: Wild Hunt on the Switch, so it's more than ready for the challenge of bringing the 2018 medieval open-world RPG to the hybrid system.
There's no release date for this game just yet, but when we hear something, we'll be sure to let you know.