The guy messed up; he failed to protect it, but we can’t also completely blame him too. Back then, he didn’t know how valuable bitcoin would be today because if he did, he should not have kept it where the girlfriend could easily get rid of it without thinking twice, just like the girlfriend can’t get rid of his valuable documents, certificates, etc. They’re two are just to share the blame; it’s not a one-sided something.
There was no faith in bitcoin from a lot of persons back then about bitcoin's potential to exponentially attain such price value as it has today, hence, a lot of early owners didn't attach that much security and value to safekeeping it neither it's seedphrases. Because even if the drive was lost, what happened to the seed phrases? Did he also lost it too or are both in the drive?!
Just as no one knows how high bitcoin prices will be today and how valuable it will be, which made them not consider it as something serious and security measures were not also taken seriously, that’s how he could have also likely forgotten to back up the seed phrase to the wallet. This seed phrase could have been used to generate another private key to regain access to the funds attached to the wallet. If he had access to such a backup, this story could have taken another shape by now; all the money and time spent in the search could have not been wasted.