He actually didn't. He, or rather his agent, knew that it would be more lucrative for him to force the Raiders to cut him and not keep his old contract with less guarantees than a new one would get him.
The Raiders made the right decision. Hopefully the Saints will too.
https://www.nfl.com/news/derek-carr-informs-raiders-he-wont-accept-trade-to-saints-release-qb