Transparency was absolutely the underlying issue. Read "Too Big To Fail" or "The Great Short" or any of the other histories of the Financial Crisis. The way CDOs were bundled and tranched made it effectively impossible for purchasers or banks to know which properties were actually covered by any CDO.

No-one knew what was in them -- the value was asserted by the ratings agencies and they were purchased based on expected rate-of-return. Even the people who went short on the market ended up using heuristics: there is a wonderful passage in The Great Short which describes a character who tells his broker that he will short anything bought by one of the people he has just met.

Once the extent of fraud became clear the entire market dumped down to 35 cents on the dollar. The fact that transparency was an issue is also apparent right here, since nowhere near 65% of consumer mortgages failed. But no-one would buy because no-one could tell if any particular CDO was backed by anyone who was still capable of making payments.

With Ethereum and smart-contract based mortgage systems this completely disappears, since the blockchain broadcasts every single payment made in real-time and it is possible for anyone to simply look and see if whether defaults are rising or falling among the mortgages that underpin their collateralized securities.