Anecdotally the risktakers have mostly left for NYC or moved overseas. The region’s best days may be behind it.
I'd say the unifying theme is pretty obvious. It's that NYC is a nicer place to live than the SF Bay Area for many affluent young people.
Now that it's less bad for their career to work remotely or at a peripheral office, why wouldn't they move to NYC?
Affluent or not, New York City does not even begin to approach 'nice'.