It is meaningless, mindless mimicry and it actually promotes apartheid, the majority overlorded by 13% of the population.
In sports, if you need a short rest, you "take a knee". Not new. Nothing wrong with it.
On Game of Thrones, the phrase was actually "bend the knee". Public submission to your master. Not part of US culture at all.
But presto-changeo! The left has worked through sports figures to promote the idea that all White people should "take a knee" in order to offer public submission to our new Overlords.
And the media pretends that it's normal and sensible and a sign of racism if you refuse.