For whatever reason, whether it's because of the nature of his murder and how it was capture on camera, or the resulting lack of action against the officers, or because it was just one straw too many, George Floyd finally became the one murdered black man where the public narrative towards his death significantly shifted, and is seen as far less divisive as past deaths, like Trayvon Martin or Mike Brown. Corporations and spineless politicians who in the past stayed mostly silent can finally speak out because the risk far outweighs the reward for them, and that's all they care about. Hence all the "brands" being active about this on Twitter.
It's the nature of the murder combined with the police response, which was to stand in solidarity with the murderer rather than quickly try and throw the guy under the bus.
For us in Australia, it's clear that there are double standards.
When that Minneapolis black police officer shot Justine Damond (white woman) dead through her car window, he got thrown straight under the bus by the union super quickly
When George Floyd (black man) gets choked to death - possibly the most personal way for anyone to get murdered - on film for like 8 minutes by a white police officer with his colleagues watching, they stand in front of his house to protect him.
If the Minneapolis police unions threw this guy under the bus, they probably could have salvaged their situation and have the racists hand wave the issue away. The fact they murdered this man by choking him for like 8 minutes straight and have the gall to stand in front of his house to protect him tells you everything about what they think about black people.