This is true but incomplete. The S&P500 is basically at the same level as mid-February, and even if expected earnings for, say, mid-2021 forward are the same as

This is true but incomplete. The S&P500 is basically at the same level as mid-February, and even if expected earnings for, say, mid-2021 forward are the same as they were in February, the missing earnings between February 2020 and mid-2021 should be reflected in prices. What's missing is that a decrease in interest rates also directly results in an increase in the NPV of future distributed earnings. That increase seems to have offset the decrease in the expected nominal (undiscounted) value of earnings. But this also makes for lower expected returns in the future: In principle, if interest rates and expected earnings stay the same, the unwinding of that discounting is what drives equity returns.