The government played a role in this by:
a) continuing the Tory policy of selling off socialised housing and/or not replacing it for rent and not to buy.
b) supporting short-assured tenancy laws, thereby making BTL more attractive
c) not regulating pension funds enough, thereby making people turn to a commodity, property, as an investment vehicle to fill in the void
d) not making certain lending practices illegal
e) many councils encouraged the building - via planning permission- of tens of thousands of small, 2-bed flats, which few people now want
f) tax laws on owning multiple properties
g) stamp duty laws
so it was a combination of banks, borrowers, government, plus some other factors that have led to the inevitable downturn.