My guess is Plataformatec did consulting work for Nubank and they are aquihiring purely for talent
This happens a lot. Direct talent acquisition with a nice payout for the talent running it.
Seems like it was a straight up acqui-hire. They were happy with the dev-work, processes and stuff they got from hiring them originally and wanted all of it. Or that was my take-away from reading it at least.
It's more like a fintech start-up trying to build a banking system that was heavily into functional program from what I could glean.