Plus, keep in mind that Google created the video. As a photographer and someone who enjoys art in general, I can tell you that it's not uncommon for artists to incorporate their name (or, in this case, their company's name) into a piece of work. It's a nice way to make the art something with which one can personally connect.
Now, I'm not saying that you are incorrect in what you perceive to be some of their reasoning for this. Of course Google wants to associate the work they do with their brand identity, and this video is indeed advertising. Anything a company does is advertising, to be fair.
That said, I don't personally believe that advertising and showing support for something are mutually exclusive. Just as a company is able to get their name out there while also donating to charity, Google is capable of spreading the Google name while also paying tribute to Freddie.
I do wonder how far ahead they plan these and what the process looks like.
Yes, this "advertises" Google, but why can't it also be a celebration of Freddie Mercury's life?
I really dislike the idea that every corporate gesture should have a sinister undertone...
