> People get rich now from companies because multiples have been artificially pushed higher by low interest rates.
No — this is not correct. In reality, multiples are driven by the company's growth rate, minus the prevailing interest rate. And while it's true that interest rates are historically low, the growth rates of today's successful companies are high enough that increasing the interest rate (from ~0% to, say, 5%) wouldn't really have a big effect on valuations.
As an example, note that Slack's 2020 revenue was around $1B, which represents an approximately 94% YoY increase over its 2019 revenue [1]. At 0% interest rates, that gets them a (very roughly) 10x valuation multiple. At a moderate-high 5% interest rate, their real growth rate drops to 94% - 5% = 89% YoY. One can argue that this should drop their multiple from 10x to maybe something like 9x. That drop is not nothing, but the reality is that it represents little more than a rounding error on the founder's wealth.
PG's point is that growth rate is by far the dominant factor in valuations. He correctly ignores interest rates in the essay because (barring out-of-band hyperinflation) their magnitude is too small to have a material effect on the conclusion.
[1] https://www.macrotrends.net/stocks/charts/WORK/slack-technol...