Everyone is a criminal mastermind after reading about someone else getting caught: You only have to say you wouldn’t do the thing that they did and you can smugly imagine yourself getting away with it.

He didn’t acquire 300 gold bars and the other currency at once. He was getting these over a long period. He works for an intelligence agency, so he knew that his actions were going to be investigated. If he was doing any of these routines suggested in the comments like buying a rural plot of land to bury them or taking up camping (alone, by himself) these are all going to raise suspicions and become another thing that could give me away.