How Sir Sharukh Got it Wrong?

In explaining U.S. or West's financial fallout, even though our professor went to great lengths, talking of consequences and root causes ,as per his wisdom; but, according per Roger C. Altman what he had to say is not correct. Roger Altman was U.S. Deputy Treasury Secretary in 1993-94.

Sir Sharukh Irfan (F. C. C. Univ.'s accounting/economics professor) was of the view that this meltdown of U.S. markets was due to the collapse of sub-prime mortgage market in the United States; and consequently housing prices collapsed and thus emerged the crisis at the surface. The same reason has been attributed by Altman, in his article in the latest Foreign Affairs magazine, as "conventional wisdom". And, as per Sir, at the root cause of financial melt-down was the preceding reason, it had various consequences we are so concerned with, naturally.

While, on the other hand, Roger said:

"This is not correct [that crisis is due to collapse of subprime mortgage market and housing prices]; these were themselves the consequence of another problem. The crisis' underlying cause was the combination of very low interest rates and unprecedented levels of liquidity."*

Roger sounds more reasonable to me and especially the lethal combination he mentioned. What is your opinion on this issue? Please do share with us.

* Quoted from, The Great Crash 2008: A Geopolitical Setback for the West, Foreign Affairs, Jan/Feb, 2009, Vol 88, No. 1.