I lack the time to fully dissect "Founder Mode," so here's a summary…
After Web 1.0, Silicon Valley focused on flipping companies as quick as possible. The motto was "grow big, fast." Like, Netscape IPO'd 16 months after it was founded.
Then Silicon Valley decided it was smart to be as big as Google when you IPO. Except scaling to thousands of employees in a few years is a recipe for disaster.
VCs will use Founder Mode to justify smaller teams, but it's mostly a reaction to the market.