If you search for "Chromecast with Google TV switches TV on automatically" you'll see that post is closed (from 2022)
While search for a solution, I found none.
While troubleshooting the issue I found that I had a bluetooth keyboard (which I gave to my kid) that was still connected to the Chromecast . When the bluetooth connection was searching for the right source, one was the chromecast which then turned on the TV. Removing the bluetooth device that might be waking the Chromecast is the solution. I hope this is helpful for others who might come across a similar use case. ~cheers
