Take your pick from:
a) They were a bit of a PR gimmick? Better for gov't to be seen to do _something_ than standing around wringing your hands and hoping things will improve...?
b) They couldn't be staffed and equipped to provide appropriate and useful additional care?
c) General hospitals were perhaps not quite as close to being overwhelmed as was reported?
There were stories that German hospitals may have been slightly economical with the truth in terms of obtaining additional funding for ICU beds, which perhaps weren't needed or even ever created[0]
[0] https://www.spiegel.de/panorama/corona-hilfen-schummelei-1-3...
Those field hospitals are surge capacity; and work with hurricanes and earthquakes where a single part of the country is affected. You can bring in volunteers and reservists from other areas to create capacity.
When the emergency is everywhere, and on-going, all of your surge capacity is gone.
But we don't do that. Instead we act surprised every time there's a surge, the media feeds off it and everyone starts infighting. I'm not convinced hospital capacity is really the problem people say it is.
Such techniques have proven to be very effective at preventing hospitalization and death for SARS-CoV-2 [1][2], yet you will rarely find anyone advocating for them.
The papers I've cited are some of the most highly cited in the literature, with world-wide support from experts at top institutions who are actually treating COVID-19 patients.
These alternatives to vaccination are likely more palatable for the anti-vax crowd, and can help prevent over-utilization of precious medical resources.
[1] Pathophysiological Basis and Rationale for Early Outpatient Treatment of SARS-CoV-2 (COVID-19) Infection https://www.amjmed.com/article/S0002-9343(20)30673-2/fulltex...
[2] Multifaceted highly targeted sequential multidrug treatment of early ambulatory high-risk SARS-CoV-2 infection (COVID-19) https://scholarlycommons.henryford.com/cgi/viewcontent.cgi?a...
Doesn't this come back (yet again) to the financial incentives?
Go to FDA.gov and read up on "Emergency Use Authorization"[0]:
> FDA may authorize unapproved medical products or unapproved uses of approved medical products to be used in an emergency to diagnose, treat, or prevent serious or life-threatening diseases or conditions caused by CBRN threat agents when certain criteria are met, including there are no adequate, approved, and available alternatives.
If it were to turn out that an existing (possibly cheap? maybe even a generic? ) over-the-counter medicine is a good treatment for C19 then that would undercut the business plans of Pfizer, Moderna, AstraZeneca and co.
Asking "cui bono" has never been more appropriate.
[0] https://www.fda.gov/emergency-preparedness-and-response/mcm-...