Just from a very theoretical level, low interest rates means the net present value (NPV) of companies, ie their stock prices, are weighted more heavily to future earnings and not just this year's earnings. So if the market is pricing in some return to normalcy, even if it's a year or two out, you wouldn't expect to see much of a hit. Assuming companies can get from here to there without going bankrupt, something the…
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.