The btc has been in the wallet since the puzzle was created
Everyone who trades fiat for crypto.
The person who created the wallets in 2015 when BTC wasn't worth much
Three letters agencies? Could be a nice way to find out if a foreign entity has an enormous brute-force capability? But more likely I'd say they got their bitcoin back when a core2duo was enough to generate a few of them overnight...
Prize pool would have to be much more than $400k to justify a state actor flexing that kind of capability, NK makes far more than that exploiting DeFi protocols.