This kind of stuff is annoying. Netlify had no need to acquire this. They just want to increase their revenue.
As a Hugo user on Netlify, I hope this doesn't affect me negatively.
I would guess its a down-round type of acquisition at the urging of Gatsby's investors and founders. They raised 10M+, this allows their investors and founders to get some liquidity back and Netlify picks it up on the cheap.
Yeah I've seen this for a bunch of startups that weren't profitable and struggled to close a new funding round. They pay back the VCs, the employees get zeroed out, and the execs usually get a retention bonus in the 6 figure range.
As some people mentioned elsewhere, the acquisition is probably more focused on Gatsby Cloud than Gatsby itself (which remains open source), and Gatsby Cloud is a Netlify competitor.