I'll defer to Occam's Razor: they probably had enough money at the outset that they don't have to worry about consistent month-to-month income.
That's not meant to be a diss. Though, given their politics, I could understand if they took it that way.
One of the two authors of the site up here, I just want to clarify before this becomes a rumour, I never worked at Meta, nor in big tech, neither have my partner.
Prior to moving on the water, Rek worked in a 10 person animation studio in Japan(Toneplus), as an animator/illustrator, and me(Dev) worked as a designer at a 15 employees company Cerego(we were building smart.fm). Afterward we worked independently making little games, got nominated for the IGF that one time, but never worked directly for a company again.
We budgeted the sailboat like this: 2 years worth of rent and related expense at our current rate, and so we could afford a 40k CAD$ sailboat. The way we looked at it was that if we managed to live aboard for over 2 years, we'd start making up the money we borrowed. It has been nearly 10 years now that we live aboard.
We're super opened with our finances and how we made this possible, so just ask us instead of making stuff up :) Cheers!