In a normal functioning democracy I would tend to agree, however, in this case the washington post itself has documented over 30.000 falsehoods claimed by Trump: https://www.washingtonpost.com/graphics/politics/trump-claim...

For this reason alone they have a good logical reason to endorse Harris.

Also, in this day and age it's impossible to be politically neutral. Especially the extreme-right makes such absurd claims that any serious paper would not publish them because they're simply untrue. This automatically pushes them into the other camp.

Anyway I think it's very poor showing that they caved to pressure from Bezos, however it's pretty clear which way the Washington Post leans. They don't need to endorse a candidate because we already know their opinion (especially in light of the list they have made above).