cause outside of Majora's Mask every home console Zelda game was built from scratch and with Zelda U being an open world game those usually take a while to make cause for example
Witcher 2 came out in 2011 while Witcher 3 came out in 2015 (4 year difference)
GTA 4 came out in April Of 2008 while GTA 5 came out in 2013 (5 year difference)