I'm gonna be honest. I don't know Garrett or Rudolph personally but I do know this. Something had to cause Garrett to go off. And it had to be something that was outside normal NFL trash talk.
Garrett was dominating the entire game. In their backfield the entire game. There's a certain kind of arrogance and confidence from being the best at what you do. And when that is inserted into America's racist history it makes some White people uncomfortable. Look at how angry Rudolph is. When you're that angry, you stop thinking rationally, and your brain immediately starts to grasp for anyway to tear the target of your anger down to your level. So what do you do/say. You call him a n*gger. With one word you can let him know that no matter how well plays, how hard he works, how much money he earns he's still just a n*gger. Ultimately, Rudolph got the reaction he wanted.
Go back and look at the clip. Myles had calmed down. Then Rudolph charged and got close to him. America's a funny place. When there are mass shootings the justice department spends millions of dollars trying to find a motive. But when a Black person is involved a crime, for the vast majority of Americans the motive is self-evident, because he's black. Until Myles announced that Rudolph used a racial slur there was no motive/logical reasoning as to why Myles swung the helmet. And no one even cared. Now they have a motive/reason and they get angry saying Garrett is playing the race card.
If the roles were flipped, the media would have spent days talking about how good of a guy Rudolph was and how it was just a mistake. They would spend weeks trying to analyze his history and determine a motive. But when the "bad guy" is black, things are very simple. His Blackness explains everything and thus the only thing to do is convict him with the maximum penalty.
*Edit - If you don't believe Myles Garrett, answer this. What caused Rudolph to get so angry and while he is that angry what is his goal? Is he just angry that his helmet got taken off, or is he angry because he feels that he's been disrespected by a Black guy on National TV...