I think they are simply maximizing the return on their investment portfolio.
They have CPAs who can give them the exact Internal Rates of Return on every investment. Since we are not privy to that info we are guessing in the dark.
"Brothers, shall we put that extra Billion into our hedge fund or into a real estate flip???????? Humm....." "Brother CPA what gave us the best I.R.R. these last 10 years?"
Added to that is the traditional Doomsday prepper mentality of WTBTS GB. Tunnels, huge back-up generators and MANY months of food storage.
(Columbia Hgts HQ exposure to a pissed off car bomber was mentioned as far back as the 70s at the home).