Your explanation would be more believable if it wasn't for the fact that YouTube and Google sheets/docs... seem to always work better on chrome with every change they make. Then Firefox catches up and with the next change chrome works better again. Now they might not make changes to specifically make things worse on Firefox, but they just don't test on Firefox. However that is very much on purpose, so it really comes down to the same thing.
Also let's not forget the shenanigans that Google pulls with ad words auctions etc.. If a person would have a history of doing things like that we'd call them dodgy or criminal, but when a company does it we somehow are to believe it's all accidents?