> no explanation on what kind of expenses those could be
I think it's pretty obvious the gold was to pay a bribe. The only thing I'm surprised about is the value. That's A LOT of money for a single pay-off or bribe. It seems more than what would conceivably be paid to an individual at once because spy agencies tend to prefer to pay-as-you-go with individuals. Each round of documents, actions or whatever gets a payment.
So I suspect this was intended to either buy a one-time, career-ending action from someone very senior or, more likely, the ongoing cooperation of a company, gang or small nation-state. It's hard to guess but looking over major events in that time frame, Venezuela might be a good bet. The odd part is that the gold was in his house. Aside from the dumb trade craft of keeping it in the very first place anyone would look, why is the gold even in CONUS?
And why gold? Bulk gold is one of the worse ways to transfer that much money. It's big, heavy, and easy to trace until melted down (which is hardly trivial for most people). But the thing I'm stuck on is the places you can walk into and get cash for even one kilo of gold, much less over 300 of them, is extremely limited - and half of them will be under some form of "Know Your Customer" reporting, especially in North America, and the other half might prefer to "Kill Your Customer" and keep the gold. Diamonds, bearer bonds, offshore numbered account, even good old Benjamins seem far better. I think the amount and medium both narrow down the sort of person or entity the intended recipient must be.
One imagines the sort of folks who'd actually prefer to receive payment in that much gold bar all reside overseas where they might control a national bank or have their own precious metals smelting operation. That's why I'm struggling to picture the fake scenario this senior executive used to plausibly convince anyone at the CIA he personally needed to take possession of more gold than several people can comfortably carry and do so in the vicinity of rural Langley, VA. I mean, he can't carry it on any commercial flight and It's not like he's going to schlepp it himself in his family sedan to put it on a secret CIA cargo flight. The CIA has people for that. Also, someone that senior isn't generally doing any direct case officer work. They manage case officers who manage field assets.
So many interesting questions we'll never get answers to.