That's not so. A lot of people were upset before Trump said anything. But hey any chance to slam Trump will be jumped on.
The thing is people don't want to be deal with the country's problems when watching sports. But not only did they interject those problems, they're basing their public stand on a false narrative about a young Black man who was supposedly on his knees, hands in the air, saying "Stop! Don't shoot!" but executed nevertheless by a White cop. Never happened but was used to tell White America how unjust and evil it is. And disrespected to many a sacred symbol when Colin Kaepernick started taking a knee. As I've pointed out before hundreds of thousands of White men have died fighting White supremacists both here and in Europe. It means something to their families and descendants.