So was he not even using a passphrase? I'm assuming he wasn't using a multisig setup.
Hard to believe someone with his level of knowledge wasn't using something as simple as a passphrase. With the large amount of funds involved
and his advanced technical expertise he should have been using a multisig setup but if not then the next best thing would be a passphrase aka hidden wallet.
If Dashjr was using a passphrase there would be little chance anyone could get access to his bitcoin, even if they had his seedphrase.
The other possibility is that he was using a passphrase but stored it in the same location as his seedphrase, but that would totally defeat the purpose of a passphrase.
Your passphrase should be stored only in your head IMO.
he did not use seeds, he did not use passphrase.
he had funds on LEGACY private key(which pre-dates seeds) on a hotwallet accessible via a server, accessible via a device which he carried with him to a conference/meetup which he (from common sense) must have allowed strangers/multiple people access or exposure to