Are you really asking?

- Primarily they despise Trump so much that they are willing to sacrifice the US in order to avoid him. (Think RINOs like the Cheneys for that kind of thinking.)

- They have little information and based on what they have heard or been told by peers honestly believe that Harris would make the better president.

- They have little information and make the decision based only on identity or some favorable media treatment.

- They have little information and don't comprehend that all presidents enact policies. This type would probably say Harris is better because she has no stated specific policies. The media paints specific policies as being fascist.

- Some people just resist the best or most appropriate solution because it's so obvious to anyone with eyes. (I worked with a guy years ago who bought a Renault, because "everyone gets a Honda Accord".) An attitude of contrarity, informed by lack of facts.