The 'Professionals' who were paid to sign off on compliance to building standards are legally and morally responsible. If we want people to be held to account then the Chartered Engineers and Chartered Surveyors who signed off on buildings despite not seeing the work that was done should all be in prison. The person who conducted the Survey that you paid for may well be one of them.
The problem is that we don't send 'Professionals' to prison in this country. It's much easier to blame developers. They are greedy and rich and don't speak with the right accent and didn't go to the right schools.
And they are rich, did I mention that? They are richer than the Professionals who went to the right schools and went to college and are Professionals... and that's unforgivable.
Bottom line; there were well paid, well trained people whose job it was to ensure building standards were complied with and they systematically failed to do their job. They are the ones who are responsible for the low standards, not the developers.