JetBrains was also founded in Eastern Europe which probably helped a lot in getting off the ground with little money as there your dollars used to go way, way further than in the west and the local job opportunities were scarce.

In the early 2000's an experienced SW dev in my corner of Eastern Europe was lucky to take home 300 USD and would not shy away form overtime as needed. Replicating the same thing in present day would be impossible as now no self respecting experienced dev here would get out of bed for less than 2k EUR take home pay and would absolutely do the bare minimum with zero overtime, or even work way less than the contracted working time.

The 90's to early 2000's was a wild west in Eastern Europe. Few job opportunities, low wages and low CoL, plus fast internet in every home, meant that everyone was hustling hard in their free time to make a great SW product using no money at all to sell on the international market and get rich.

Now things are different here. Plenty of great paying jobs at established western companies or startups means that the people here are more likely to just want to work at random big corp or new startup for good pay and WLB rather than put 50h+ workweeks in building their own product at home like their predecessors did.

My point is that JetBrains was more of an exception by catching a great wave in time and space that can't be replicated today.