Rejected Photo with technical issue - which mistakes are serious?

There are several points in the "Technical FAQ" which may meet my photo, but I really don't know which of them leaded to rejection. I hope, somebody can tell me more.
I will describe the possible points:
1. I used my drone "Mavic 2 Zoom". Perhaps drone cameras are not good enough because of poor lenses.
2. I took videos instead of photos and extracted this picture from a video. Perhaps too bad resolution and compression.
3. The horizon was not horizontal. For better quality (IMHO) I resized the picture to 400%, turned it by 1°, cut the triangles off and resized the result back to the original size 3840x2160 which means increasing the original resolution by about 3,3%.
4. I separated the sky and increased the contrast of the landscape three times a little bit, each time more and more concentrated to the horizon.
5. To make more details visible in the dark areas, I increased gamma and adjusted contrast and brightness.
6. I increased the contrast of the separated sky.
7. To meet the taste of most people (IMHO), I increased the saturation of the whole picture a little bit.
OK - which point was wrong and which point was acceptable?
left picture: original - right picture: final result (rejected)