That's for "if absolutely nothing happens to prevent it" and a lot has happened since that was written
1.7m represents 100% of the population getting infected at the same time, and nobody getting medical care (from what I've read, 5% of cases are requiring ICU intervention, 1.7m is 5% of the usa population)
Given that since then, the US has taken huge steps towards total lockdown, statistically we've already shifted dramatically towards the lower end of the spectrum
An interesting video from a mathematician, which points out that small changes in behavior have significant changes in both how flat the curve is and also the total number of cases
https://youtu.be/Kas0tIxDvrgHowever, you are correct, there *are* estimates that high. If you want to invest in a funeral home mutual fund, don't let me stop you, though be sure to get out before the short term drop in demand, as it's just being pulled forward