Can't transfer large original video file from iPhone to PC without huge compression.

So I used by iPhone as a B-cam the other day, as the device is being touted as a 'pro' camera. I was happy with the quality of the footage on the phone, but when I plugged my phone into my PC to transfer the file, I could see shorter videos and all my photos in the DCIM folder, but not the long video (25 mins and 9GB in size). It just doesn't show in the folder at all. And in the folder properties, the size of the folder indicates it isn't in there - but it is!

I have since read that there is some sort of restriction on videos over 4GB or 15 mins that might have caused this.

Anyway, I have located and tried to wirelessly transfer the file via iCloud, OneDrive, Simpletransfer and VLC and each time the file gets unavoidably compressed to only 4GB in size and looks awful as a result.

How can I easily just drag and drop the file off my phone and why is this so hard to do?! What's the point of having such a great camera if it's so hard to share the content in its full splendor?!