Expanding hospitals, building new hospitals and training scores of new highly-skilled staff all takes many years. In addition to being extraordinarily expensive.
And then what? The pandemic ends and we have incredibly expensive facilities sitting empty (but still incurring maintenance costs forever) and a surplus of highly-trained staff who cannot find jobs because 98% of the time, we simply don't need any more capacity than we had in 2019.
Training staff does take time but new hospitals can be built quickly. The Chinese built an entire new hospital in 10 days. It probably isn't as good as a modern US hospital, but it's better than nothing.
And then what? The pandemic ends and we have incredibly expensive facilities sitting empty (but still incurring maintenance costs forever) and a surplus of highly-trained staff who cannot find jobs because 98% of the time, we simply don't need any more capacity than we had in 2019.