Well, yes, it's a business decision. Google wanted to push their Chromecast devices so they made them use proprietary Google Cast protocol and removed Miracast from Android (both phones and TVs). They later added Chromecast/Google Cast to Android TV but it is still not supported on other platforms. Samsung on the other hand had their own TVs which don't use Android TV so they added Miracast back to their phones and removed Chromecast so that their consumers would buy Samsung TVs.