Twitter crops rather than rescales posted images to some 'interesting' subset of an image that doesn't fit the preferred aspect ratio. So, the person behind this account created an antagonistic situation: made a very tall, thin image with Mitch Mconnell on the top and Barak Obama on the bottom, and another with them swapped between top and bottom. In the initial post, the cropped thumbnail shows Mitch Mconnell for both. The thread has two more situations, one with the ties (red/blue) flipped and the colors inverted. The only time it 'prefers' Obama's end of the antagonistic image is with inverted colors and him on top.

Twitter has an algorithm to pick which part of oblong images to showcase in the feed. People have been posting examples where, given the "choice" between a white person and a person of color, the white person is always picked, regardless of orientation or where they are in the picture.

This was noticed in a thread about how Zoom's background detection seems to not work great for people of color, and how the WebEx cross-talk protection seems to favor men over women.