You were filming in very low light conditions. Dusk, cloudy, sun low on the horizon, contrasty. With filming into a sunset/sunrise, you have little choice but to expose for the sky, leaving everything else essentially black/silhouette. Your sunset videos will look better when you're flying lower so you have some silhouettes to contrast against the sunset and provide drama as you move past them. Don't expect to get good exposure on trees and ground plane when flying/filming into the sun. After flying into the sun, turn the drone around, change the exposure and you'll get the trees on the sunny side. The challenge is that to get proper sky/sunset exposure, you have to use a dark ND filter otherwise, the sky/sunset is blown out (blown highlights are basically unrecoverable), but when you're flying away from the sun, that dark ND filter is gonna force a higher ISO (and more noise). So basically, you can't have it both ways. To get the best image quality in dusk/sunset lighting, you have to land and switch out your dark ND filter with the clear one in order to get proper exposure on the sun-lit subjects. It's a pain and it wastes precious daylight time, but that's the reality of filming.
It's always a balance where you have to choose what's most important to have at the proper exposure. There's often a wide exposure range shooting in mid-day sun. When filming or photographing, whatever you chose for proper exposure should fill most of the frame, so if the sky is really bright, frame the shot with minimal sky. If you're exposing for the sunset, use the silhouettes and movement to create the drama.
Take some time to learn and use manual camera settings at all times. Did you set the aperture and shutter speed yourself? In terms of order of priority: Set shutter speed to 1/50 or 1/60 (depending on frame rate); Set aperture between 2.8 to 5.6 optimally (smaller apertures 8 and above are not as sharp). Set ISO as low as possible. If it's darker and you're already at f2.8, you'll have to go to ISO 200 or 400. Noise can be corrected in your video/photo editor to some degree. More difficult with video.