Personally, I have always believed that the Democrats expected to lose in 2020. That's why all the younger and more ambitious candidates dropped out before Super Tuesday in favor of a senile old retard who was old news in Washington 20 years earlier. He was supposed to be the 2024 version of Bob Dole.
It was the COVID fiasco -- which began almost immediately after Biden effectively secured the nomination -- that even made the 2020 race a contested one. In some ways, the timing couldn't have been worse for the Democrats.
Notice that they've been calling this the "Biden/Harris administration" since even before January 2021.