OK, so why is this even an issue? No crime committed, nothing to see here, move along.
Assuming this is an individual IRA and not a SEP (the #'s still don't work with a SEP) can you create some example where contributions of 6k a year (the current maximum allowable contribution if you're over 50) can turn turn into 100,000,000
I think it's likely he rolled it from another retirement account (maybe his 401k from Bain) but even those types of accounts have limitation on contributions
The only other answer is a return on investment that is almost impossible to comprehend but then again maybe he had IP0 stock that he got for pennies that are now worth $400 a share or something like that
The questions being asked are definitely valid but I suspect they won't go anywhere