That's not what the article said. It was highlighting how despite some hospitals being overrun, these field hospitals still went unused because there were no plans in place to utilize them.
We didn't flatten the curve enough to make these hospitals useless. We simply didn't use them despite needing them.
That's a gracious reading. If there had been an absolute need for more beds, plans would have been developed to make use of the space.
Instead, it might imply hospitals were dealing with increased load, perhaps needing more beds than they had but not so much of an increased load to justify implementing and following a plan to use these facilities.
We didn't flatten the curve enough to make these hospitals useless. We simply didn't use them despite needing them.