Two things make this different:

1) There's record unemployment in the US and there's an active pandemic. People are unhappy and the country is a powder keg ready to go off.

2) The footage this time is especially graphic. You can see the officer strangling George Floyd with his knee. You can see the unnervingly satisfied look on his face. You can hear George call out multiple times that he can't breathe. Then, after he stops moving you can watch the officer continue to strangle him for four minutes. You can also see three police officers that stood by and let it happen in the background. There's not much wiggle room here.