I agree, that didn’t make sense on its surface. By definition, liberalism and fascism are at odds. According to Wikipedia,

Liberalism: A political and moral philosophy based on the rights of the individual, liberty, consent of the governed, political equality, right to private property and equality before the law.

Fascism: A far-right, authoritarian, and ultranationalist political ideology and movement, characterized by a dictatorial leader, centralized autocracy, militarism, forcible suppression of opposition, belief in a natural social hierarchy, subordination of individual interests for the perceived good of the nation or race, and strong regimentation of society and the economy.

Now, if I had to guess at what OP meant, perhaps it’s that America’s Liberals are more closely aligned with its Conservatives (who are not all fascists yet but are rapidly embracing fascism over the past decade, probably longer) than they would be with pure leftists (as in full-on Socialists/Communists, which Bernie, a Social Democrat, is not). Best recent evidence I can think of for this is the DNC actively colluding against Sanders in the primaries of 2016 and 2020 and consciously omitting leftist policy from their platform in 2024, instead replacing it with moderate Republican policies.

In short, I believe mainstream Democrats would endorse Republicans if it meant keeping a true leftist from power.