Anyone can use a blockchain explorer or buy a cyberforensics tool and it's not been the first time that crypto has been seized. They 100% did not crack the SHA-256 algo, but the server the private keys were stored on. FBI said they were investigating since last year and found 90 other ransomware victims, so that's pretty much the tell that this has nothing to do with BTC itself. Also Darkside was not the initial attacker, they sell ransomware as a service. Most likely the attacker made a mistake and got caught. Nah dude
Wild conspiracy theory: the Darkside hacking group was actually an undercover FBI operation to begin with. The government wanted to bring public scrutiny to ransomware, and kickoff the "War on Crypto" Just today it came out that the encrypted chat app Anom, used by criminals worldwide, was actually a FBI honeypot! https://www.engadget.com/fbi-encrypted-chat-app-anom-criminals-102001487.html Actually pretty funny checkout their homepage https://www.anom.io/ You can enter your phone information and see if you're wanted by the FBI https://www.abc.net.au/news/2021-06...d-crime-bust-an0m-cash-drugs-murder/100197246
Honestly you love to see it. Likely the hackers didn't use a cold wallet, but a hot wallet (a browser wallet on their laptop). The US gained access to the device and took the private key. It happens all the time, which is why Ledgers and Trezors exist so keys can be taken offline. It's akin to a hacker either keylogging or phishing your bank account password.
An interesting thought. Basically all it would take to end all crypto is one step function advance in computing that only one party has access to which enable them to successfully mount 51% attacks. No need to hack anything, just use the blockchain's foundation against it. Not what happened here, but worth thinking about for those talking about replacing national currencies with crypto.