It's common in liberal circles these days to imagine the absolute worst possible outcome from Trump winning, and then assume that their nightmare is based on verifiable facts. When in fact it is based on conjecture, with a heavy dose of fear-based prejudice.
That's not to say Trump isn't an absolutely awful person, who would make possibly the worst president we've ever had, but that is only a educated guess.

I could be wrong. President Trump might just be a normal, bad president, like we've come to know.
I don't pretend to know the future, but it's now common for liberals to claim they do.
In fact, just doubting the validity of some liberal nightmare scenario on TOP will get you flamed. In much the same way that doubting the danger of Saddam in 2002 would incur accusations of treason in Republican circles. Hyperbolic doomsday predictions are now accepted as facts in the liberal echo chamber. The more hyperbolic the nightmare, the more credibility it is given.

Critical thinking is being trumped by fear.

It's now common to summon the specter of Hitler when talking about President Trump, when it fact Silvio Berlusconi is a better comparison.

His promises to sell off his personal assets to avoid conflicts of interest were never fulfilled, which sparked controversy throughout his terms in office. Berlusconi is a controversial figure in modern Italian politics: his tenure as Prime Minister was racked with scandalous sex affairs and poor judgement and decision-making.
According to journalists Marco Travaglio and Enzo Biagi, Berlusconi entered politics to save his companies from bankruptcy and himself from convictions

Doesn't that sound familiar? It does to me.
It's bad. It's embarrassing, but it's not scary.
Let's look at the other end of the spectrum. Why isn't Trump the new Hitler? For that, I refer to this article.

Gupta characterizes Trump’s campaign — correctly — as a “proto fascist” movement, meaning embryonic fascism, which may or may not develop into a fetus, let alone a baby. Proto-fascism has the DNA necessary to develop into a fully developed fascist movement, but without organizational sustenance and ideal conditions, the embryo withers.
While Gupta is right to warn of the threat, he overstates its imminence. A Trump presidency would feed the fascistic fetus in some ways while likely poisoning it in others.
A comparison of Trump’s campaign to the Nazi movement is helpful to illustrate. German fascism was a genuine, organized mass movement, with the Nazi party becoming the biggest political party in Germany. The party also had a massive paramilitary wing, the “Brownshirts,” which at its height had three million well-organized troops.
When Hitler came into state power, he brought with him his personal army, a massive political party with its own distinct, powerful ideology.
Trump doesn’t even have his own party, let alone a real movement (an electoral campaign is not a movement). His ideas are rudimentary and inconsistent. Because of him the Republicans are deeply split. Trump joined the Republicans out of weakness, not strength, and weakened the Republicans in the process.

Trump has no unified message or ideology. Ego has its place in fascism, but not without a framework around it.
The conditions also have no comparison.

The establishment, however, doesn’t arbitrarily dabble with fascism; they use it only when necessary, since engaging with fascism causes political and economic disruption, making profits less predictable.
Historically, a large section of the establishment opens its arms to real fascism when they literally fear for their life. Fascism is the “nuclear option” for capitalists, who use the far-right ideology to prevent the Left from taking power, so that capitalism can be preserved, and with it the large profits for the wealthy...
The German establishment needed Hitler to save capitalism, which was in imminent danger of being overthrown by the millions-strong and growing Socialist and Communist movements, led by mass organized parties.
The balance of power between the establishment and the working class was nearly even. Consequently, the establishment could not rule effectively. Protests were numerous, employers were under attack with strikes, and pro-capitalist reforms could not be implemented without risking insurrection.
Hitler and the German establishment were in total agreement that the Socialists, Communists and the trade union movement were too powerful, and had to be crushed. The first inhabitants of the concentration camps were leaders of the Left.
The situation in the U.S. is nowhere near 1930’s Germany. The U.S. establishment doesn’t yet need Brownshirts to save capitalism. Yes, widening inequality is an inherent and growing threat to U.S. capitalism, but a new Hitler isn’t yet required to smash the Left. This dynamic is ultimately what will prevent a President Trump from being too large a threat in the immediate future.

Since liberals have decided to ignore class, they've also forgotten that fear of communism was the primary and secondary reasons for the rise of fascism, not racism.
Deciding to ignore class is also the reason why liberals are clueless when it comes to understanding Trump's popularity.

On the other hand, there could be silver-lining from Trump winning.

If Trump becomes president, the various social movements — labor, peace, immigration, women, LGBT, Black Lives — will be given free reign to fight back by the Democrat-affiliated media and politicians, who will all discover the backbones they lost while Obama was in office. Good media examples are Jon Stewart and Stephen Colbert, who were brave pit bulls against Bush but toothless puppies under Obama.
In this sense, a Republican president can open space for the Left, even as they attempt to implement policies against it, while Democratic presidents shut off political space. Under Obama, protests were discouraged. Challenging politicians with bold demands was prohibited as the working class was told to defend Democrats from the right wing. Politics was stifled.