My Chromecast is connected to one of the many HDMI inputs on my receiver. There's exactly one HDMI cable going from the receiver to the TV. So... the Chromecast woke up the receiver which then woke up the TV (good!) but the receiver was too dumb to switch to the device which woke it up.

The receiver, a Pioneer Elite SC-25, was pretty cool stuff when it was introduced in July 2009, having a then-huge number of HDMI inputs as well as cool-running class-D amps. Today, even the cheapest receivers have lots of HDMI inputs, and have been getting rid of everything else. The latest Pioneer SC-7x series seems to be pretty much the same, in terms of the audio section, with better video processing, and an Android/iOS app to let you configure and control the thing. And the prices are lower. That says that if my receiver blew up, I'd replace it with the current model, but I'm not spending that extra coin just in the hopes that they fixed HDMI-CEC.