Why "taking a knee" has taken off so strikingly

It's interesting to note how the phrase "take a knee" has gained currency during the police brutality protests this last week or two.
This is not not the "bend the knee" of Game of Thrones, which indicates submission and swearing fealty to a victor. This is not "kneel before", which is more an act of supplication or worship in a religious context. It isn definitely not just plain "kneel down", which is a practical everyday action performed when gardening, laying a carpet, washing the floor, etc.
To "take a knee" seems to have a specific African-American context. It has an (African-American-dominated) American football connection, where a player catches the ball and then immediately kneels to hold up play as a kind of semi-legal means of wasting time and counting down the clock. But it also has a more honourable history with Martin Luther King Jr., who was sometimes described as taking a knee when he led impromptu prayers in the street or on a demonstration march.
And then it really took off with the Colin Kaepernick-led protests against racism in sports and elsewhere, when individuals, and eventually whole teams, would go down on one knee during the pre-game national anthem back in 2016 in protest against the treatment of minorities in Trump's America. In this context, kneeling is a mark of protest, of challenge, of being unwilling to stand just because everyone else is standing, and more specifically of opposition to the status quo in modern America, and to the veneer of patriotism that conservative philosophy often hides behind.
It is very much in this mould that demonstrators are taking to their knees to protest against police violence in the aftermath of the death of George Floyd. And very effective it has been too - everyone from police chiefs to health workers to US Senators to German soccer players to Justin Trudeau have been very publicly taking a knee. It is not so much a mark of respect to Mr. Floyd who, whatever the unfortunate circumstances of his death, was definitely no Martin Luther King, even if he has become something of an unlikely martyr to the cause of black outrage. It is more a dramatic and unifying action that brings protesters together in a common cause. As I see it, it is not exactly a pose of respect, or if it is, it is respect for the cause rather than for any one individual. In this particular case, it also has the additional connotation of mirroring the police knee that held down and ultimately killed George Floyd.
I have a suspicion that most of the kneeling protesters have not rationalized the activity - it just seems to be the right thing to do at the time, and it does admittedly have a striking dramatic effect all of its own. And I think they have Martin Luther King and Colin Kapernick to thank for that.