The Legend of Zelda: Tears of the Kingdom is the most popular game of the entire year so far and is selling incredibly well, and as it turns out, the game was finished about a year before it was released earlier this month.
According to an interview that The Washington Post did with series producer Eiji Aonuma, the game was actually scheduled for release last year in order to "make sure that everything in the game was 100 percent to our standards". Aonuma also spoke about the trailers that were released about the game, and the reason they decided to drop a demonstration video explaining the basic concepts around the game:
"People had not gotten their heads around the gameplay elements or where the fun might be."
This likely doesn't come as too much of a shock. The Legend of Zelda: Tears of the Kingdom is a game heavily reliant on physics, and physics is famously difficult to get right in a video game. Bugs and glitches can completely destroy physics-based gameplay systems, so to have a game as polished as TOTK is an incredible achievement for the team over at Nintendo, and for Eiji Aonuma himself.