For years, Democrats, with their Trump Derangement Syndrome, failed to accept Trump's presidency and continually framed him as a monster, fascist and a threat to American democracy. There's no doubt they bear the blame for creating the environment in which such an assassination attempt could take place.
If anyone is responsible for creating an environment of violence in American politics, no one is more responsible than Trump. Be it his anti-immigrant rhetoric, his failure to condemn hate crimes or the fact that he failed to accept he had lost the election, encouraging supporters to storm the Capitol building, there's a long list items in which he is the one stoking divisions.
There's a 75% chance that Donald Trump will be elected US President in 2024, according to the Metaculus prediction community.