There are some very real issues around crime and mental health in the United States running in multiple directions, but it’s just not remotely true that prison (or crime) one-to-one replaced the old mental institutions.

Among other things, if you look at who was in mental hospitals before de-institutionalization it’s 47% women and 20% senior citizens at a time when the national age structure was much younger. This is not the crime/prison demographic at all.

There are both people cycling in-and-out of prison who need mental health help and people on the streets who might benefit from coercive treatment but the old institutionalized population was way bigger than that and included lots of elderly people, Down’s syndrome cases, etc