And no, it wasn't because of a huge fee.
Nor was it the dope new set.
Rather, Will has admitted he was won over by a lack of rules on what he could wear on the TV.
Discussing The Voice UK's switch between BBC and ITV, Will said: "I was a bit torn at first. I didn't think I wanted to go to ITV,that's where The X Factor is and I thought I was BBC for life.
"I was worried the commercial breaks could kill it, too.
"Then I was told I could wear whatever I wanted."
Will explained: "The BBC had so many rules about what we could wear!
"I'm going to slim down for the live shows, so I can wear things I look really good in. You're going to see me in tank tops, no more baggy clothes."
And Will also said he planned to get back on his phone once the live shows rolled around again.
"I like to be on my phone because it means I can communicate with a wider audience," Will said. "There are plenty of people out there watching the show while also looking at social media on their phone and laptop. It allows me to talk to those people."
The Voice UK 2017 blind auditions continue this Saturday night at 8PM on ITV.