However, when we look at how much effort the feds put in to get these BTCs, I wonder if they have some personal agenda against the Dread Pirate Roberts? The man is in prison for life, but they are still after him, or rather his BTC.
It's too much money to scoff at given how disproportionately little effort is required to get a hold of them (often all it takes is a single mistake). DPR could probably contest this seizure since it covered the criminal fine ('restitution') multiple times over but in practice his chances of succeeding would have been near non-existent. The same goes for the 70k BTC from 'Individual X' from 2020 who apparently also managed to hack SR.
Those files don't close until everything is settled, they will keep investigations and men and spend thousands of dollars even if years have passed and the actual thing doesn't matter anymore, the FBI has tens of cold cases that are decades old, highly probable the culprits are dead and they are still searching for them or for the money.
It's the same with Alphabay, Alexandre Cazes has died in prison 5 years ago, and investigations on the money and the relatives still made a few headlines till 2019, and it might be possible the actual investigation is no way close to being finished, in 2020 they sentenced a moderator to 11 years in prison, and they are still
after the sellers that were active there.
Yes, this happens with all DNMs if there's any actionable evidence, in some countries authorities have even gone after individual buyers purchasing for personal needs.