No it wasn't. Again he's done more for the causes he believes in than most. If it solely about attention, he would have shelved it to get back in the league. It cost him millions of dollars.
https://www.instagram.com/p/CAq3fpCgyve/?hl=en
Just to show how much influence athletes have. The meme of "This is why we kneel" that was shared by Lebron James had over 5 million likes. He has over 65 million followers on Instagram as well. Its not a stretch by any means to see people emulating those things in protest.