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If blockchain itself could be hacked, then hardware wallet also wouldn’t be a safe, because when you connect it to a network, you could see that there aren’t any coins in it.

Hot Wallets have been hacked, hardware wallets have only been hacked with access to the device itself. I actually read about a man hacking into his own Trezor on here. Long read, even longer hack....

This is true. A massive amount of computing power would be needed nowadays. It would require a state actor making, then verifying a double-spend. More than 51% of the network would be needed, but only for a short time.