that’s not a theory... what you made was an obvious observation. a theory goes to the “why”. at least in this case.
OK then, I'll venture a guess: we're dealing with a 12th Century mentality that values religious purity over material well-being. It would appear that a sizeable percentage of the Iranian population would not agree with their nominal leadership.
Bottom line: It would not occur to the ayatollas to 'invest', except in 1 area -- nuclear weaponry. That's Ahmenajahd's function: he's the technocrat. The interface between the ayatollas & the physical world.