Given the current thing going on with the pokaymans cards I would doubt this guy is an obsessive collector seeking his personal holy grail.
A friend managed to sell his small assortment for something like 5 grand earlier on this year. And that was to an acquaintance who buys and sells stuff like this as a side hustle. After that guy had done the work in identifying, grading, and selling each card individually they apparently brought in over 6 grand.
The cards were nothing particularly rare or special. He was just old enough to have gotten the cards when they first came out in the US, then not played with them much. So early cards, in good condition with some reasonably desirable things in the mix. And I know a bunch of people in our age block who were actually into Pokémon who got a lot more out of it, one friend ended up having a down payment for a house in his storage locker.
So probably speculation.