"people will just change it back to Google in the settings"
My friend you do not know people.
My friend you do not know people.
People will happily use the default search engine, no matter what it is, and believe that it's Google they're using, unless the search engine goes out of its way to tell the user that it's using something else.
People don't read error messages, people click away whatever gets in their way, people don't even notice logos.