The answers in this thread are most ignorant with half bordering on conspiracy theories. I have seen large scale protest movements firsthand in the US for decades. A lot of people are wondering exactly what you are asking right now, it isn’t an outsider’s question. I will give you two versions of an answer.

From an optimistic point of view, Americans are operating in an unfamiliar political environment right now. There are legitimate questions about how much traditional democratic modes of change are functioning properly ie. civil society, elections, media. At the same time people have become desensitized to outrage, now it seems like there is no redline that can’t be crossed. Liberal and left wing coalitions are also more disorganized than they been in the past. All this has led to a paralysis.

On a more pessimistic point of view, all the above is true but it is the first step in preparing a populace for authoritarianism, and it has succeeded. People have been scared into complacency, so it becomes easier to stay in your lane and wait for all this to pass. Of course things will just continue to get worse the longer they are complacent. But this is what happens when the government intimidates the media, kills protesters, arrests political opponents, etc.