Nobody knows how this will end, or when. Could be months, could be decades.
https://static1.squarespace.com/static/5386693ce4b05d183bf2d...
Fundamentals try to explain and predict valuations; they don't dictate them. Only supply and demand, within the constraints of the market, can control valuations. And to be pedantic, price discovery is faster and tighter today than ever before, and that's part of the reason we have so many lively derivatives markets.
The problem, as you aptly point out, is that this price does not fit any model that is blind to the rates component of equity demand. The word "untethered" is totally appropriate for what's happening in the market; there's a disconnect between price action and corporate earnings growth because there's demand for equities in general when everything else yields almost nothing.