Photoshop will only import the first 500 frames of a video.
If your video is more than 500 frames, you need to perform multiple imports - Frames 1-500, then frames 501-1000, then frames 1001-1500, etc. Once you've imported the frames, you can move the video layers to a single document and reconstruct the timeline.
That gif is 500 frames....
That gif is set to play once. You need to set to
Forever in the Timeline Panel or the Save For Web Dialog if you want the gif to loop.
The loop the gif is performing can be done less than half the frames. You only need to astronaut to pass once... then repeat.
A ~4.8MB gif is ridiculously huge in terms of size.
.. shrunk to 300px... and only 224 frames.. looping.... (580k)
Unless there's some other animation which I can't see in your gif, this would be sufficient.
If you keep the original size (1080px).. the resulting 224 frame, looped, gif is 2.4MB in size. Which is still quite large.