Those young(ish) campaign staffers have no notion on the significance in history. They all learned calling some one Hitler is the highest form of disparaging slanders from their (non)education.
As for Biden, he reads every line fed to him.
Actually if you research the 1944 and 1948 elections you will find that both FDR and Truman called Tom Dewey a fascist. And Dewey was a liberal Republican who accepted much of the New Deal. After that it became de rigueur for the Dems to call every GOP candidate for POTUS a fascist, though I don’t recall Carter or his campaign doing so to Ford.