Where would all the extra doctors and nurses come from? I know when it originally hit NY, a lot of medical people went there from around the country so they had a staffing influx. But now there are surges everywhere. You can build what you want, but it has zero value without the trained staff to run it and you can't manufacture them on any fast track.
London built (repurposed a building more like) a 4000 bed hospital early on, but only treated 51 patients before they closed it down. The meds there said they were nuts as they could never have staffed it, but it looked good.
Anyway, COVID was always going to spread, every lockdown has been and is about slowing it so that things don't get overwhelmed. Treatment has improved no end and fortunately vaccines are now rolling out.