It's strange to me that the author doesn't mention the primary cause of all homelessness, which is housing insecurity. By the numbers in the article, something like 99% of people with "severe mental illness" are not homeless, suggesting there are workable options for people with mental illness that don't require mass institutionalization.

I'm not sure if it's an objective of the "Manhattan Institute" to spin up these institutions for indefinite detention, but I will point out that providing housing universally is definitionally cheaper than institutionalization, which is housing with paid orderlies, guards, service workers, etc. If providing housing is too big-government, eviction protections were seen to curb homelessness during the pandemic. And for these right-wing think-tankers, housing affordability also has an available "market" solution which just requires the loosening of zoning restrictions with little other public investment.