I highly doubt they did anything remotely like "hacking" the seed phrase. I don't care for cryptocurrency, but I hate cop bullshit even more, so here's my 2 cents.
or just found it written somewhere in the house?
this one.
A seed phrase is just an encoding of a long binary number which can be used to derive the secret key. Trying all the possibilities probably isn't possible, and I think it's also unlikely that they found a way to weaken it. What they probably did is find it and type it in. They DID raid the dude's house, where he was probably keeping a copy of it.
"Twenty or thirty years ago, police did not hack, that was not a thing that they did, but that's very much part of the bread and butter of a modern police force nowadays," Mr Uren said.
LMAO fuck off with this. I don't doubt they have some tech guys on hand. I don't think they have access to the quantum computer you'd need for this.