Is it normal that muscle mass disappears so quickly?

I once had a noticeable six-pack, broad shoulders, upper arms of over 18.8 inches and a chest that could have been seen from afar under a dark shirt.

Then I messed up and hurt myself pretty badly. I couldn't train for a long time and got into a psychological dilemma because this fact wore me down. I eventually started abusing alcohol and taking drugs. This was like 5+ years ago.

Today I'm still not weak, but I don't look like a hunk anymore.