At the risk of sounding catastrophist, the difference between Obama and Trump is that Obama is Obama and Trump is Trump.
Even if you disagreed with Obama on every issue, you could see that he had a sense of personal conviction, morals, and love of the country. Whatever he may have done that upset you, you could atleast be assured that he was doing it because he genuinely thought it was the right thing to do. You could say that about almost any president.
Trump is unlike anything this country has ever had before. He has no convictions. He only has his self interest at heart. He praises authoritarians, and he praises them because their authoritarian. And he gained the presidency through fostering the support of deplorable and maliciously minded people who hate minorities, refuse science, and are happy to game systems they purportedly believe in when it's to their advantage. All headed by a part who already is happy to practice unconstitutional ways like gerrymandering to maintain power.
I don't know what America will be like after Trump, but trying to go "hey, don't worry guys, trump will never X" has proven time and again to be a temptation of fate that whatever higher being there is seems eager to indulge in. This feels like yet another iteration of the 'both sides' argument. "We were catastrophists and were wrong, now your catastrophist, so your wrong too." No, you were wrong about Obama because you were being a fucking idiot and making shit up. I hope we're wrong about Trump, but we're using actual facts to make our assessment of him.
Being a catastrophist sounds an awful lot like being a realist right now.