Or, and this approach gets rid of the victim complex you seem to have, they recognize a truth that every good player of OW knows: Tanks were and are the most powerful role in OW. They are the closest thing to a carry this game has so when Tanks are what win games, by such a significant margin, you can afford to tone down the power of tanks without the role itself losing that power.
Also, your victim complex basically ignores a large swath of DPS nerfs that hit earlier this year, but as that doesnt fit the narrative I guess I can see how you would choose to ignore it.