Keep in mind that your lowest shutter-speed is 1/25 (not that low, but perhaps as low as you want it in a flying platform -- debatable). But your aperture can also get wider, and there is Auto ISO.
I'm getting to realize that the DJI Hyperlapse feature is really just Timelapse (there is a difference)..
To get the exposure smoother exposure throughout the sequence with normal (land-based) timelapse, we take all the shots to individual stills (not video) and we DO INDEED change exposure during the sequence (as it gets darker, you need to increase the exposure or you will get a very dark ending, as you did). Of course, that makes for a choppy sequence, exposure wise (it will be obvious playing it back).
So if you're really serious about this, you will a) save the shots to DNG and b) also get software to smooth out the exposure jumps.
My recommendation is
LRTimelapse. This also requires that you have Lightroom. With these two, you can take your stills and not only enhance the images, but smooth out the exposure ramping.
Cheers, Chris