"What kind of perspective is involved here? If these are institutional investors, aren't any of them in it for the long haul?"

I would say this is now the beginning of the next Bull Market. In next decade you will see unbelievable amount of volume- and the market is going to going up and down a lot, but it's mostly going to scream upwards.
My guess anyhow. And of course Fed probably suspect this so, the fed rates will go higher. And Oil will drop. And Gold will drop. Dollar will be stronger. And will see this in next couple months. Of course, if there is major civil war in China or somewhere, all bets are off.