I agree to an extent. What caused the collapse of the US housing market in 2007 were non-existent or weak lending standards for subprimes around 2002-4. Those subprimes would end up entering delinquency by 2006-7, with a default rate of around 23%. Prior to 2002-4, the delinquency rate for subprime loans was around 7%. So something happened to the standards for subprimes around 2002-4. Also, not helping the matter, was that the number of subprimes issued jumped from around 110,000 a year from 1993-2003, to about 266,000 a year from 2004-6. So there were tons of more subprimes, with relaxed standards, that were inevitably going to enter delinquency as soon as the introductory ARM rate expired.
They actually made a movie about it called The Big Short that I would recommend.