Trump did not "politicize" the NFL kneeling situation. The kneeling players did that when they kneeled, knowing that their actions were in national media spotlight.
Actually the Defense Department started down that path with that paid-patriotism pimping scandal. Inasmuch as nothing about a national anthem or any of that rah-rah jingo shit has jackall to do with a sports event, that's how football (and other sports) got politicized in the first place.
Then more specifically some reporter with time on his hands who himself was failing to follow the robotic jingomurmur decided to photograph Colin Kaepernick --- who had been just quietly sitting down for weeks, making no noise --- and milk a fake "story" out of easily-swayed drones who can't be bothered to think about the paragraph above. So that happened.
Then later after it petered out, Rump -- who never passes up an opportunity to milk the emotions of the gullible,(which is what I just pointed out in my first post here over which you soiled your diaper) stirred the shit up again in his insatiable quest for attention to Numero Uno (which, again, I already articulated in direct response to the OP) in freaking Alabama. And that put the players on defense. And they held.
So you are correct that Rump didn't start it. He just milked a dead horse. That's what opportunists do.