If we have 1k dollar BTC then we will think about buying a hardware wallet to give more security to that BTC.
There is nothing such as '1k dollar BTC', these are two different currencies that you have just sandwitches together, you should rather say you have 0.027 BTC or $1 worth of BTC.
But he didn't put his coin in a careless wallet, Bitcoin Core 25.0 wallet is a full-node wallet and is considered to be one of the safest wallets.
BTC core is only a safe wallet when it is run in an airgapped device, just because it is a full-node wallet does not mean it is safe by default, if you run BTC core in an online machine and in an unsafe enviroment, your funds are prone to hacking.
Its ability to download and validate the entire Bitcoin blockchain makes it one of the most difficult wallets to attack.
This is not true. BTC core is a full node wallet and you can download the blockchain and verify everything locally, this protects your privacy and also protects you from connecting to malicious third party nodes, but it does not secure your funds from hackers or malware or from every form of online attack if you use it in an online machine and in an unsafe enviroment.