Also, consider that a lot of what hedge funds offer is bespoke risk profiles to high net wealth individuals that are overexposed to particular market sectors.
The issue, as you imply, is that in a bull market people lose almost all ability to exercise reason and view the opportunity cost of capital as the S&P.
But a lot of hedge funds aren't running high levels of beta, and investors in their funds don't demand that (unf for some hedge funds, who demanded low vol and then went into index funds when beta did well).
And, ofc, most equity hedge funds have had very strong performance. All the Tiger group hedge funds have private companies, everyone owns tech companies, you are even seeing value hedge funds in FAANG stocks...it is quite something.