Trump is the symptom. He has exacerbated the situation, definitely, but he is not the cause.
Speaking purely about proximal causes, we are witnessing the outcome of thirty years of hatred, misinformation, and agitprop to exploit divisions that were set in motion principally by Newt Gingrich. The 90’s saw America’s partisan division really begin, and right-wing media poured gasoline on the fire. The stupidity, partisanship, and acrimony people used to appeal to Republican voters reached an apparent Nadir in 2009. Racists accused Obama of being a Muslim, McConnell deliberately implemented the strategy of obstructing everything Obama ever did, and the McCain campaign somehow found in Sarah Palin a charismatic moron who appealed to the fuckwit demographic. Trump just jumped on the bandwagon of hatred and stupidity, and rode it to the White House.
I’d throw in a few other things: The abject failure of the Church and decline of religion, an era of peace and prosperity that caused people to grow up without existential threats, the total failure of our schools to instill critical thinking skills and civic education, and that orgy of celebrity, conspiracy, validation, and trolling that we call the internet.
Speaking about ultimate causes, that goes back even farther. Reagan’s misguided media deregulation set the stage for the rise of the Fake News network, while Reagan, Nixon, and LBJ all played a part in spreading the idea that government was an adversary rather than a beacon. The 1964 Southern Strategy actively recruited racists and the religious right to the Republican party, and that could, in turn, be traced all the way back to the Civil War and - earlier still - the founding of Colonial America.
So no, Trump didn’t cause any of this. He was just the loudest and most aggressive in his willingness to take advantage of the American voter’s contemptible stupidity.