I wrote a long post about this and then lost it, which is probably just as well as I was quite annoyed by some of the opinions expressed here.
For a start, prisons aren't just full of rapists and murderers. I have a good friend who spent a big chunk of his life in prison, due to drug addiction. All small sentences but they added up to a lot. His crimes were always possession or shoplifting, to feed himself or his addiction. He managed to go through heroin withdrawal through sheer strength of will, plus support from, ironically, some other junkies. Nowadays, he doesn't even touch alcohol or cigarettes. He makes no excuses for his crimes but I doubt he would have seen the inside of a prison if he hadn't been an addict.
Secondly, my DD and SiL work with the homeless. They say that nearly every rough sleeper they encounter has substance abuse/mental health issues, and most have been in prison at some point. DD and SiL try to get help for them but often see them sliding back into addiction or mental distress, or both, due to lack of ongoing support. Then they start re-offending and they are back inside. It's a revolving door.
If conditions have worsened in the prisons, this is only going to inflame the situation. People already tend to come out worse than they went in. It can't help society for prisoners' mental health to deteriorate further. It's usually bad enough already.
Rehabilitating prisoners doesn't mean forgetting the victims. The goal is to reduce the number of future victims. I am not blaming prison officers either. My DD works in co-operation with the local prison, trying to reduce the number of ex-cons ending up on the streets, and says the officers are struggling with underfunding and overcrowded conditions.
This country has a massive drug problem and the methods we are using to tackle it aren't working. I am not saying that everyone in prison is there because of substance abuse, but a lot of them are. It's no good demonising addicts - their lives are messed-up and they are doing what they can to survive. Until we find a better way of dealing with the problem - which means more funding, and maybe treating addicts as patients rather than criminals - our prisons will be full of them. Then there are the mentally ill. Our mental health services have been cut and cut, and the help that's needed just isn't there. More candidates for a cell. Isolation because of the virus must just be adding to the stress.
Another long post. Sorry!