Yeah, but look at their cash positions. I posted an analysis [1] based on their published financials in another thread; basically their revenue could go to zero and they'd be fine for a year and a half. With a more realistic 75% drop in revenues they'd be fine for about 5 years; with a 50% drop in revenues they'd still be profitable.

[1] https://news.ycombinator.com/item?id=22884042

Isn’t this a result of good governance, ie no stock buybacks?

That's one factor. Also great margins, a disciplined acquisition strategy, monopoly position, an inherently labor-efficient business model, and a shrewd prop-trading desk.

FYI they've been heavily buying back stock

Their revenue will suffer, but they have lots of cash. They are prepared to weather the storm.