I'm taking a guess at a few reasons, and I would primarily suggest that we have severely under-invested in mental health solutions to prominent problems for quite a long time (addiction treatments, social care, parental courses, but mainly: research).
Without motivation, projects like that rarely take off the ground as they're tied too many years of negative finance.
I recall a few countries have successfully tackled drug/addiction>theft, homelessness - reducing petty crime substantially - via dedicated teams separate from police forces. I'm sure you've seen this type of successful solution too.
We just ain't seem to be bothered..?
In terms of the country being in the middle of a mental health crisis... is it? I guess maybe progression in society has allowed a more open discussion, giving more people information they simply never used to have back in the day. But isn't that just better identification stats?
We have to differentiate between the mental health issues that are actually an epidemic and have viable working solutions against the random nutters who would struggle to be identified anyway (apart from the Jihadis) until after the fact. Oh yes, and the daily trending mental health disease.
However, I chat a lot of **** so who knows hey?