First, none of us are Satoshi. Second, since he was the creator of Bitcoin, no one knows better than him how Bitcoin works, how to best secure it, or anything else about Bitcoin.
He didn't keep all his Bitcoins in just one wallet. Blockchain researchers estimate that Satoshi kept his Bitcoins in about 22,000 Bitcoin wallets. Since there were no hardware wallets at that time or wallets like Metamux, Eletrum, or the like, he kept them in his own Bitcoin Core.
And speaking of hardware wallets from different companies, yes, I have a slight suspicion that since a second party is creating a wallet to store Bitcoins, they might have some secrets.
If the person you are storing your assets in is a thief, it probably won't be too hard for them to open your box.

I think he is disconnected from the internet, which saved his wallet. Since he is the founder of Bitcoin, these exploits appear to be happening on smart devices. Ever heard of your feature phone getting hacked? Never heard of it, right? I think the same applies to Satoshi himself.

Your wallet is safely storing your Bitcoin, but your internet connection and device are not safe. So hackers try to exploit those and get access to the wallet easily. Also, we don’t know exactly how Satoshi managed all the keys. Their coins remaining untouched could simply mean the keys were never exposed, or they chose not to move them.

"You can use physically isolated Ubuntu 16.04 or versions prior to Windows XP SP3," Kleiman said.