This isn't two people working on it on the weekend as a hobby project that got too much attention during an unforeseen event.

Rather, it is two people who worked on it as a full time job (no other sources of income) from grants for three years (with funding running out this year).

For a rough estimate, one would expect about 10,000 hours have been put into the project (2 people, 2000 hours a year, 2.5 years).

It is less of a hobby project than Minecraft was in 2012.