This video was released by the police department.
Are you suggesting someone from Uber drove down to the scene at 10pm, somehow managed to grab the SD card from the dashcam with all the police there, ran back to their car, uploaded it to their laptop, fired up Premiere, edited the brightness, downloaded the modified video back into the SD, ran back to the scene with the tampered evidence, and only then the police got to it?
Sorry, but if this isn't a conspiratory theory, I don't know what is.