Imgur started redirecting direct media calls to their website based on the referral header.
Basically if you didn’t visit the imgur site recently they will redirect you back to it when trying to directly view an image or video.
Fix it with this Firefox Plugin: https://addons.mozilla.org/en-GB/firefox/addon/imgur-redirect-blocker/
Used to. It took a single registry tweak to enable it which was easily found, but still a pain.