- after 2008 Great Financial Crisis
- actual startup, not spinoff from larger company
- financially successful exit
- early non-founder employees made a substantial amount of money?
There were also suddenly a lot of people without a home to sleep in, and suddenly a lot of homes on the market.
Basically, right after a crash is the best time to do anything.
It's harder to know from acquisitions, but I'd guess that most of those with sale prices >$1b generated ~10-250 non-founders with $1m+ share packages. I think that the Qualtrics founders said that they minted 250 millionaires from their initial sale to SAP.
(Not lost in all this: over the years the tax treatment of option grants has changed! It used to be a hugely advantageous way of giving employees something of value, and that's been eroded a lot.)
Amazon had north of 100,000 employees by the time I joined in 2012. The "plucky startup" days were long gone, even if they did still tell the fable of the door desks at every orientation class